LizO:
Depending upon how much time you have between flights, you might not be able to research in San Francisco. (You might spend too much time traveling to and from the airport.)
There is an LDS location that my father used and because they have local records, that might be one choice. I will find it's location (it is in or near San Bruno).
I will have a look around to get additional ideas.
In the meantime, this might be helpful:
http://www.sfgenealogy.com/sf/sfranlib.htm-----------
The Family History Centre is located:
975 Sneath Lane, San Bruno
According to mapquest, it is about a 10 minute ride from the San Francisco International Airport. I don't know what the history centre currently has, but years ago it contained quite a bit of information for California researchers. (We aren't American, so we didn't use local records.)
http://www.familysearch.org/Eng/library/FHC/frameset_FHC.aspAt one time, the FHC in Oakland required reservations to use the equipment; I do not know if reservations are still required, or if they ever were required in San Bruno.
It looks like the NARA and History Centre are about two minutes away from each other, by car.