Here's my two cents as a recent grad of med school (take it or leave it)..
It seems to me that the prestige of a school is unlikely to make up for deficiencies in your med school application. It is true that some schools are more "prestigious" or whatever, but the great equalizer is the MCAT. So you need to do well on it, which entails learning your bio, chem, and physics well the first time around. In my opinion, this means going to a school that you are confident will give you a good education - you can discern this at least in part by asking about medical school acceptance rates.
I chose a smaller state school for undergrad for several reasons. First, I knew the school was strong (despite the fact that it is not terribly well known outside of the region) in biology, particularly for pre-meds. The smaller size afforded me the opportunity to get to know my professors and therefore get what I assume (based on interview comments) were very strong letters. The smaller size and lack of a significant graduate student population also allowed me to find a research position fairly easily. And finally, the scholarship I received (and the cheaper price tag overall) left me with minimal undergrad debt. Considering that I attended a private med school and my current debt is around $200,000
eek
it helps not have another $200,000 from undergrad.
My opinion is that if you want to get into med school you must 1. do very well on the MCAT, 2. make excellent grades, 3. participate significantly in medically oriented extracurriculars, 4. do a good amount of volunteer work and 5. establish good relationships with professors (not just TAs) so you can have someone go to bat for you on your application. Prestige of an undergrad school I think becomes more important if your dream has always been Harvard Med. But otherwise, do the above plus probably some praying/voodoo/whatever you do and don't come across as the type of person who likes to kill kittens. Where you go is less important (in my opinion) than what you make of it.
Take it or leave it. Good luck to you!