I think Obnoxious Dad brings up a lot of relevant and important points here, but the one thing I will disagree with him on (as I have before) is that you should avoid colleges where your ACT/SAT fall below the 75th percentile. I would say maybe if you're below the 50th percentile, it might be cause for concern, but, depending on the 1) college and 2) medical school, you /will/ get a boost for going to a better college. How much this boost affects your application and whether its worth it is up for debate, but I don't want you to turn down a place like Brown or Duke to go to your next door state school for the sole reason of thinking you won't get into med school at these places. Now, not every medical school will care where you went to college, but as
@efle likes to point out, on a longstanding AAMC/AMCAS survey (which can be found in the essential compilation of SDN wisdom link in my signature), adcoms at private colleges marked selectivity of undergraduate institution as an important factor. Now, if you go to Duke/Yale/whatever and fail to perform well, yeah, you're likely going to be in trouble, but its likely that if you aren't performing acceptably there, you wouldn't be the "rockstar" of your state school either.
Now, there are perfectly valid reasons to choose your state school over a top college, but they go well beyond what is essentially portrayed as "I shouldn't go to Penn with my 2250 because it's not at the 75th percentile". That's a silly way to go to school and at this level of competition, SAT scores aren't going to be able to differentiate individual performance in college - that will come down to a whole host of other factors.
One other thing I might note is, if you are somehow able to see how many students continue onto organic chemistry from general chemistry, be aware that at some schools, gen chem is the weedout course while organic is the weedout course at other schools (and then at still other schools, both are weedout courses). A better statistic might be to look at 1) how many students who apply are accepted to medical school 2) does the premed committee screen applications 3) what percentage of the class comes in as premed. Some of these statistics are hard to find for some schools, so don't worry too much if you can't find them.
Ultimately, you should be going to a school that you feel you can do your personal best at, regardless of prestige or whatever. If you are in an environment where you can excel, everything else will likely fall into place. Fit matters.