ahh I dunno! I'm actually tentatively pre-med too, and I believe the majority of med schools require one year of calculus in college, so that means you could either take 1a and 1b or 1b and 53 (multivariable calculus). When did you last take calculus? I took bc in my junior year and although I got a five on the ap test, I honestly don't remember anything, so I think I'm just going to take the 1a, 1b sequence, and then take 54 over the summer because differential equations are really useful.
Based on what I've read from here and ratemyprofessor.com <--my new best friend, your other classes are very do-able, so maybe it'd be best to get 1b (a yucky weeder) out of the way now. Also, since you've taken two years of calculus, you have a pretty solid foundation in calculus, and it probably will all come back to you with just a little summer review.
good luck with your decision!