AM or PM ?

It all depends on personal preference and when you have the time. I prefer to exercise as early as I can, but only so I don't make excuses to not do it throughout the day. Some people think there are added benefits to exercising at certain times in the day, but any time is better than none at all, in my opinion.

If you exercise AM then your blood sugar will be low if you are exercising very AM, i.e. before breakfast. Consequently your body has to work a little harder for the same output so in theory you'll burn more calories. But, it's best to do low intensity work at this time of day due to the low sugar levels.

Whenever you are most likely to do it on a consistent basis.

Some folks prefer morning, some afternoon, some the evening. Some people eat before a workout, some don't. Some people eat right after a workout, some don't.

There are "studies" that will say why should or shouldn't do any of the above. So really, the only "right" answer is the one that you'll find works best for your schedule and body.

Personally, I work out at night during the week, due to my work schedule and typically the afternoons on the weekends. But sometimes I wake up early and get it out of the way in the morning if I have the time. And, of course, there are race days, where my races usually start around 7am, which is earlier than I even wake up for work on normal days. According to my BodyMedia Fit and my HRM, I don't burn any more or less no matter when I work out.

Good luck and have fun!

There is no right or wrong time to do exercise just do it when you can.