When are you planning on applying to medical school? Right after your junior year? Give yourself as much time to study as possible. What you don't want is to be in the spring semester needing to take the MCAT so you can gets your apps in early and not feel fully prepared for the test. Then you are faced with pushing off the test and thus delaying your application, or going for it and risking a poor score. If I were you I would take this Spring to take care of anything that might otherwise take a majority of your time in the summer (not sure what that would be, but you'll want plenty of time come study time), find some solid prep material, and come up with a mcat study schedule that you are committed to. Once summer comes, buckle down and study, register for a test date toward the end of summer and shoot for that. If by the time your date rolls around and you aren't feeling 100% yet then ease your fall semester a bit and keep studying. Bottom line is you should be prepared when you go in on test day. You'll probably be fine after a summer of studying, but at least this way you have a little cushion. Then you'll have all spring to take whatever classes you want and focus on putting together a solid personal statement. I'm not sure what your science background is, but I felt the genetics on the mcat could be self taught without too much difficulty.