Ok, I'm not quite sure why I'm back here to argue with a kid in HS, but something inside me cringes when I see bad advice being given out...
First off, I did not "insult someones intelligence" as you suggest I did. I asked merely, at the age of 17 or 18, how you've gained any such perspective into college and med school. Having, say, completed college myself, I think I have the right to question your so-called knowledge of things when you clearly are off base on a few things.
As for classes building on each other: yes and no. For chemistry, absolutely you need gen chem 1 for gen chem 2. For biology, it's another beast entirely. As long as you have some fundamentals down (say, from your AP bio class) and you meet the pre-reqs, if any, you'll be fine. For example, my 400 level Translational Genetics course required none of the same base knowledge as my 400 level Wetland Ecosystems course did. I have no idea why you say upper level biology courses are a bad idea for med school-in fact, I would say taking them makes your app stronger and helps with preparation for the MCAT and beyond.
Ultimatley, for the OP, I would say pass out of any lower levels you can because they are the weed outs-with the caveat of only doing this if you are a strong student. If you are not a super strong student, then take the lower levels because the upper levels might leave you behind, real fast.
Here's the reality, folks: AP credits will make you lives infinitely easier in college. They will allow you to take fewer credit hours during orgo, fewer hours while studying for the MCAT, go abroad where you want (and not have to worry about things transferring), and allow you take classes that interest you beyond the intro level. You might even be able to graduate early-especially if you get an early acceptance to med school, you can bail out and earn some money.