I can't really help you find a GOOD doctor, but I can at least help you avoid Nick Riviera.
For CA, try
here.
It lists their medical school, so at least you know whether they went to a US school or Guadalajara Correspondence School of Medicine.
It should also list if their license is current, although I've yet to see a doctor on there that listed anything negative for that, so I guess unless they've had their license revoked, you likely won't see anything (ie if they've had a few malpractice claims, they probably won't show up unless he lost his license as a result.)
Another page from the same site is
here. It has a link to look up board certification, although I haven't used that page personally, so no idea if it's any good.