Need help selecting a bike

$250 is a hard price point to hit. Really hard, even for used, without going the department store route.
At 6ft, you are between a M and L frame, so your best bet is to ride one of each and see what feels the best.
If I were you, I would seriously consider saving a few more bucks and upgrade to a better selection of bikes.
For instance, you could probably pick up a used Canondale Quick CX3 for $400-$500 bucks pretty easily.

I second this. $250 is really not going to get you a very good bike. The lowest prices I've seen on a decent bike is in the $400 - $500 range. It's not like when you were a kid and you could get on any bike and ride it. You will be uncomfortable on a bike that doesn't fit or a bike that has cheap components. Spend a little more and get a decent bike.

How much are you riding? Department store bikes are fine most people (though I do recommend taking it to a bike shop to make sure it's correctly put together and everything is tight/aligned/etc), but if you're doing a lot of riding or are thinking about anything competitive then you'll probably outgrow it pretty fast.

Dept store bikes are heavier and come with lower quality components (biggest difference is they don't last nearly as long). But if the weight isn't a problem, then go for it.

You MIGHT be able to find a workable bike in your price range - it'll probably be a late 80s/early 90s lugged steel frame with downtube shifters.

You probably fit a 56. I'm 6' 0, and depending on the company, I fit a 56 or 58 (my Specialized is a 58, but if I bought a Trek, it would be a 56. My TT bike is a 54, but that's a different animal all together).

Downtube shifters were used on most road bikes until 1990 (really cheap bikes had different, weird shifters). In 1990, Shimano came out with STI brifters, but it took a number of years till they came down to all levels of prices.

There were some very nice bikes in that time period. The problem is that in the last few years, many were bought up by hipsters and turned into fixies, driving up the price of the market.

It is not that $400-$500 is an issue, I just don't want to commit to a bike that I am not 100% confident on using for a long time. I am not sure if biking is just a passing hobby or something I'm seriously enjoying.

I'll let you in on a little secret--the more you spend, the more likely it is that your bike will fit you well and work reliably, which will make you want to ride more. And knowing that you invested a bit more into your bike is added incentive to keep up the riding. You may find that you want to do more riding and even some competitive stuff once you start riding...that was what happened to me and a lot of other folks I know.

Touche!

I'm going to be spending a lot more on the bike now aint I!

Check some independent bike shops in your area. Sometimes they take in trades and can get you a deal on a used one or at the very least, give you some direction on what to scour Craigs list looking for....

I bought my bike new from a bike shop and they asked what I planned to do, and didn't try to oversell me at all. In the end, I spent less than I had expected to and still LOVE my bike 6 years later.

Go to 1 or 2 bike shops and have them fit you for a bike. They should measure you and ask you what you intend to do with it and suggest a particular style. Once you get an idea of what size you need, hit Craigslist and monitor it for bikes. You could probably find something decent on there if you are patient.

If nothing else, post a wanted ad or something for a free bike that someone wants to get rid of.. I rode a crappy bike all Summer last year as I saved up for a $700 bike I too wanted to be sure that it wasn't a passing fad, so I told myself that when I ride 100 miles, I'll get a good bike... well, I couldn't afford the "good bike" until I was about 650 miles in on the crappy bike. But, I'm glad I did... I learned to tweak the turd bike and made it do what I needed it to do until I got the good bike. After riding the good bike for another 700-800 miles, I get on that old bike and don't know how I did it... Only one thing comes to mind: I wanted to ride, so I made the best of it.

There are lotsa $50-100 starter bikes that you could get from people who bought a turd bike and never rode it. That can tide you over til you get the cash you need for the bike you want. Don't be picky, just get something and stop renting bikes.

Good luck!! and enjoy

Like others have mentioned, if you "cheap out" and get something that doesn't fit right or doesn't hold up, you'll be a lot less likely to ride it. You're absolutely not going to find something good at a department store. Almost of those bikes, even though they look similar, are toys and they are not made to hold up over time. There are a lot of shortcuts taken in the manufacturing and component selection to hit those low price points and they aren't obvious at first glance to someone who isn't familiar with bikes.

The best thing to do is just not think about price at all for now. Go to some bike shops and ride some nice bikes. You'll know when something feels great. Hopping on a bike that begs to be ridden is a very gratifying way to spend your time and you'll never regret the purchase. When looking at new bikes, you'll find the best value with Tiagra equipped bikes... that (or arguably the more expensive 105, depending on who you ask) seems to be where the price/performance ratio is most favorable. You can also get by with Sora which is even less expensive, though the shifting controls may seem a little cludgy after a while. Then again, you can save money that way and if you find out you are really into it later you can upgrade the drivetrain. The great thing about bikes vs cars as a hobby is you can do all the work right in your living room!

One thing to know about road bikes and components, is that after a certain point you're actually paying more for less. Literally. The highest priced lines like Dura Ace don't offer any appreciable performance enhancement for mere mortals like me, and the cassettes, chains, etc wear out a lot faster. The advantages they offer are very minor, mostly in the weight department and some subtle improvements that you may or may not feel with the shifting. Yet many of those components are double the price, or more, than the Ultegra line which is the next highest group.

If you have a bike shop that sells used bikes, that is probably a great place to start. Be careful with craigslist though unless you know what you're looking for. It wouldn't hurt to take someone that knows about bikes with you to look at it (just like when buying a car). Don't buy anything that doesn't fit right. It will drive you nuts!

Windsor is a brand used by bikesdirect.com. Though a lot of people will tell you to steer clear of bikesdirect, it's actually a great value when buying a road bike - provided you know what you're doing. In your case, you'd want to take the box directly to a bike shop to have them make the final adjustments and inspect every part for proper operation. Bikesdirect.com has such low prices because they literally slap them together and don't really do all the final adjustments, and sometimes parts aren't properly tightened to spec, etc. That's why it's important to take it to a competent bike mechanic before riding it. Not just a buddy who has some tools either... often the bottom bracket will not be tightened properly or the rear derailleur's stops will not be set and those could be serious, even dangerous problems if overlooked. You will also want them to go over the wheels and make sure they are properly tensioned and true.

Not trying to scare you off of bikesdirect... it might be a good way to go in your case. Sizing is critical so find a road bike that fits you at a store, go online and check out the geometry and sizing for that specific size, and try to match those dimensions when making your purchase. There's a lot more to consider than just the standover height too... reach is important to get right.

The Windsor Wellington seems like a good deal, it has Sora shifters and derailleurs which aren't bad for starting out. I assume this is the bike you are referring to? http://www.bikesdirect.com/products/windsor/wellington2_IX.htm

If you do go the bikesdirect.com route, you'll definitely want to arrange the shop who's going to look at it ahead of time and make sure they're cool with it. Most decent shops should be. Any bike shop that will only service bikes they sell isn't really a full service bike shop if you ask me. That's like a muffler shop only working on cars that were bought in their parking lot. Makes no sense.

This is the one I'm looking at: http://boston.craigslist.org/gbs/bik/3003117869.html

The problem I see with that bike is the by first glace it looks like a department store special.
It looks like a road bike, but the technology is old.

You can buy the bike brand new for only $269.00 here http://www.bikesdirect.com/products/windsor/wellington1_IX.htm
It has down tube shifters and low quality components that will not be nice to ride for very long.

you would be better off with this
http://www.bikesdirect.com/products/dawes/lt_dlx_xiii.htm

or if you can swing it
http://www.bikesdirect.com/products/dawes/lt2300_xii.htm