Thanks for all your responses. As I mentioned, we're only going to be there for a couple of days, so we're concentrating on the high profile tourist stuff in downtown SF. Following the advice from many sources, I'm going to avoid getting an expensive car (parking, etc.) and stick to public transportation. The only wrinkle that has produced is that I just realized that the BART doesn't run until 6AM on Saturday and 8AM on Sunday. So it makes it hard to get a 6:15 departure home on the weekend.