Former ROTCer here, albeit with the Army, and you should drop ROTC if your goal is to go straight to medical school after college.
I'm not entirely sure how the Air Force handles this, but you can rest assured that they will have a say in whether you get to go to medical school. Best case scenario is that they give you an educational delay, which frees you to attend and pay for medical school how you see fit. Worst case scenario is that you have a medical school acceptance in hand and the Air Force doesn't let you go. A "middle" route might be that you get to go, but they require you to accept HPSP, thereby doubling your obligation. Free yourself from the whims of DoD bureaucracy; getting into med school is hard enough without all that.
Besides that, you're right - the time commitment to ROTC can be considerable, but it gets you in sneaky ways too. My ROTC lab and course were only offered once a week, and they come in several hours chunks. Those become big black holes in your calendar when you're trying to schedule other classes. My GPA suffered because I had to take difficult professors and/or courses I didn't find interesting just because they fit around my ROTC commitments. Haggling with my cadre when it came time to scheduling interviews was fun too.
If you still have the itch to serve, then HPSP will be there. In the medical corps, beginning from the first day of intern orientation to the day you separate/retire, precisely no one will care one iota that you did ROTC.
