Hi Susan, I'm originally from SF, it's a GREAT city, not too big not too small with lots to do! I live up in the mountains now but whenever I go to SF for a visit I stay at the San Remo Hotel, built for workers after the 1906 earth quake, it is charming and NOT too expensive for SF prices. Here is their web-site: http://bayarea.citysearch.com/E/V/SFOCA/1000/03/42/4.htmlThe other great thing about this hotel is it is located just a few blocks from Pier 39 and the cable cars. Parking isn't far either if you have a rental car (parking is a pain in the neck in the city, be warned!).
Here is another good site to help you plan your trip: http://www.sfgate.com/
If you need any more help in planning and what to see in what amount of time I'll be happy to help, we do this every year for my husbands German relatives so I have it down to a science! Just let me know how I can reach you. Cheers! Nancy