Train for Two Events?

boxingday2010

I completed my first half marathon in December and have been doing cardio since then (either an hour on the elliptical) or 6-8 mile runs, etc. But I was thinking of doing another Half Marathon on May 12th (so I'd start training first week in March). However, the sprint triathlon I've done the last 2 years (and I'd like to do it again this year) is on June 23rd. So maybe this is a dumb question but can you train for two events at the same time? I'd get a month of straight half marathon training in March but starting in April I would also have to start my training for my triathlon (meaning adding in swimming and biking into my training). Will that 'mess' anything else between the two events? My thoughts were, it is all cardio work anyway so I'd still be 'training' for my half marathon, right? Just wanted to get everyone's thoughts on that or if you think it is best to just focus on one event and not 'overlap' my training.
Thanks!