First, let me tell you I was never in the Marine Corps, but I did wear some MARPAT once. :mrgreen:
In all honesty, with any branch you join you're going to be hard pressed to find time for college within the first year. Remember that you'll have your intial entry training (basic/boot) and your job school. That's roughly six months gone there, give or take. Then you have to get settled into your unit and for the first stretch of time you're going to be very busy taking what they taught you at your job school, brain dumping it, and learning how to really do the job. Before you know it, a year is gone.
Let's also not forget that we're pretty involved in a war right now, deployments are not a matter of if, but when.
As for a two year enlistment into the Marine Corps, they only have three year enlistments and that's for infantry (that was true last year). The Army has an 18 month enlistment, but that's for infantry too (any other MOSes Army guys?). The Army also has 2 and 3 year enlistments, but they are MOS (job) specific. AF is 4 so is Navy (I think). So pretty much, when you look at coming in for such a short time you're going to be balls to the wall working. Combat Arms (infantry type jobs) will keep you very busy.
Someone else mentioned the National Guard, that's a six year commitment, but it's part-time outside of deployments. That would probably be your best bet since you want to go to college while you serve. They have some great programs for guys that are enlisted and want to become officers, plus a lot of states offer tuitition assistance.
Is it worth it to join the military? I'll give you an resounding "hell yes," but ultimately it's up to you and what compromises you're willing to make in your life to accomplish your goals.