If your primary reason for joining the military is money for school, the general consensus that I've seen on the military forum (and my own opinion) would be a resounding "DON'T DO IT!" If you have the mindset of joining the Air Force, or any other branch, primarily with the intention of serving your country and think of benefits such the GI Bill merely as added perks, then I would wholeheartedly encourage military service. But if you join for the money then there is a strong possibility that you will be hating life for several years. I've seen it many times with younger service members that were suckered in by a recruiter to join for college benefits and were utterly miserable.
Don't get me wrong, though. Military service CAN be extremely rewarding and an opportunity for personal growth and development. But you HAVE to go into it with the right mindset. Basically, you have to be willing to completely put aside your medical school aspirations for several years and focus on serving the military. After your commitment, you can resume your med school pursuit and then enjoy the benefits that you've earned. There is a lot of variability in military service and yours could afford you opportunities towards your goals, but often you have little to no control over it so best to have no expectations and pretty much prepare for the worst.
Another point to consider, as others on similar threads have mentioned, if your ultimate goal is to become a doctor then those years of service will translate to years of lost income as a practicing physician in the future. Depending on your specialty and the med school you attend, this may equal or even surpass the debt of a medical education. In this case, those years of service had better been about more than the money.