We have stayed in San Francisco many times over the years, Most of the time we rode our motorcycles and finding some where to park was not a problem, (well except for the security issues). What I do know is most of the hotels have parking garages. Those with open parking the spaces are tight. I sat and thought about it for a while and I just can't think of a hotel or motel with a large open parking area. I could only think of the parking lots down by Fishermans Warf that a rv could park in and then walk or take a cab to a hotel.
I will make a call to a friend on S.F.P.D and ask him if he has any suggestions. If I come up with something I will PM you the information. San Francisco is a fun place to visit,