You'll automatically get a license through the hospital as a consequence of training there. You will have to get a permanent license at some point, and it will be an expensive hassle (6-9 months, fingerprints, lots of paperwork). At UCSF (and I assume other UC system hospitals), they have a "licensing fair" once a year where they bring in all the required services (state clerks, fingerprint machines) so you can automate the process. From what I'm told, UCSF actually pays for your CA license (for residents; not for fellows, sadly).