As the previous posts have suggested, this really depends on where you live. Unless where you live depends on where you train. Every airport except SFO (and maybe San Jose now) has at least one flight school. Usually more than one. Sierra Academy at OAK used to be a fairly large organisation, good place to blow a lot of cash and prance around in epaulettes on the way to your c172. ( I should know I worked there a long time ago).
American Flyers have a school at Hayward (just down the street). Again a place to blow a lot of cash.
Personally I think the best schools are the ones on the west bay (palo alto etc..). I had a friend who instructed for an outfit over there and he loved it. He said they were extremely good school with nice airplanes. If you are looking to just get a private license though you could save an awful lot of money by not going to the bay area. go to Concorde or somewhere outside the bay where airplanes are much much cheaper to rent. The further away you get from the big cities in CA the more money you will save.