If you want a school that teaches to the MCAT, go to Xavier (xula) aka Newsweeks hottest school for premeds. The UC's are not good about that since they're public and just don't care. Since that's not one of your options, all three of these schools will prepare you extremely well for grad school in general.
As UCSD biochem alumni with friends at all the UC's and lots of engineering and bioeng friends, I've had the chance to get opinions on these 3 schools. (You can also get a lot of these opinions by lurking on the SDN forums for a while)
Berkeley: Most recognized name in everything in a location with a lot of potential for bio and bioeng internships while you're in school. On the downside, lots of berkeley premeds complain that its hard to distinguish themselves from their classmates when it comes time to apply for med school, and I think (although I could be wrong) that they have the worst stats of the three for having their students accepted. That being said, when I interviewed at UCI's MSTP, there were 4 or 5 berkeley students, 1 or 2 from UCLA, and 1 other from UCSD. Also, great on campus atmosphere, but really expensive off campus housing, and don't bring a car.
UCLA: Great name in everything, but for the size of Los Angeles, there's less of a concentration of industry for internships. Although I'm sure you can find a lab on campus. UCLA premeds seem to complain the least about getting into med school, but I'm not sure how that translates with Md/Phd programs. Great on campus atmosphere, but pretty expensive off campus housing, and you need to bring a car.
UCSD: The name is still a tiny bit less prestigious but Newsweek's hottest school for science for a reason. It is a bio and engineering powerhouse with professors that, for the most part, love cheep lab labor in the form of undergrads, and there is a ton of industry providing internship opportunities within a 5 minute drive from campus (Reason why I chose #1 why I chose UCSD over Berkeley). Our premed's and Md/Phd hopefuls fair alright, but everyone complains about the on campus atmosphere. Off campus housing is moderately expensive for CA, especially being in La Jolla, and you will probably need a car (I like my car so reason #2). Oh yeah, and its the closest to the beach with the best weather (reason #3).
Hope that's helpful.