San Francisco has a pretty good public transportation system. To play tourist you'll need more than a couple of hours. Personally I'd try to find a CG near a hub to the BART and use public transportation to play tourist then come back to my trailer, get a good nights rest and then continue on with my trip. Driving into San Francisco I'd be concerned with wasting my time sitting in traffic and find parking once I got to my destination.
Just a thought to ponder. When I ran long haul I drove by and only saw most things through the windshield. So many times, while I was there, I never really got to experience being there. My goal now is to actually visit the wonderful places I drove by. I did manage to drop a trailer and visit Mount Rushmore. The attendant looked up at my tractor, didn't miss a beat, declared "pickup with a camper, $7, park over there". These days with satellite tracking, I could not get a way with that. My point, you took all the time and effort to get there. Take the time to experience it.
Good Luck and safe journey.
