i took the mcat yesterday w/o 2nd sem phys or ochem. i studied like hell for the past 6 mos w/every type of prep material under the sun. i had tpr, kaplan, aamc, berkely review, examkrackers, nova, even rea. i had like 20 practice tests (of which i took about 5). i even had textbooks that i went over.
here's what i thought:
tpr physics materials ROCK. i learned a great deal from them and they totally simplified the horrendous 2nd sem stuff to the point where i intuitively understood the material. they explained everything from scratch and it was very easy to understand.
another thing: the mcat isn't SUPPOSED to historically rely on 2nd sem stuff, although it's fair game. that is, it's really rare that you would get an entire 3 passages on capacitators, light/optics, magnets, etc. but they would show up on discretes. i got lucky yesterday and had all 3 in passages.
it wasn't pretty. at the same time i don't think i totally bombed the passages b/c a lot of the ?s just ask you pure passage-based stuff, so you have to learn not to get intimidated by the weird formulas you've never seen. w/o the classes, on ALL the pract tests i took (III, IV, VR, VIR) i got above 32s. i thought i was pretty ready for the test....but after yesterday we'll have to see.
okay, so to cut this rambling short, it depends on how much time you have to prepare and how smart you think you are at self-learning. obviously you will need to dedicate your entire 3 mos of summer to studying 2nd and 1st sem stuff. why take it in august when you can actually take the classes, have your summer off, and take it in april w/everyone else? unless you're trying to apply this year. in which case i'd say go ahead and take it w/o 2nd sem stuff.
good luck whatever you decide.