Bill, if I were you, I'd also make sure I had a few days extra, rent a car and drive from SanFrancisco down the coast, through Santa Cruz, Monterey, Carmel and down through Big Sur. The scenery is nothing short of stunning!!! Very big problems driving though: drive 100 feet, be amazed by scenery, pull over, get camera out, take pics, get back in car and keep doing this over and over and over hundreds of times!!!!
Public transit throughout SanFrancisco is pretty good, in fact, they've even got some old TorontoTransitCommission streetcars down on the Embarcadero!! *LOL* I heard the sound, turned around and sure enough, one of my old "Red Rockets" right there in CA. The BART system is good for zipping around, and you can even download a BART program for your palm pilot which makes things a lot easier, ie timetables, exchanges etc.
Just a word of warning though, further to Ricky's post: They do close the GG bridge to foot traffic at a certain time at the end of the day. In January, it was 6:00 pm and they are VERY strict about it, including loudspeaker warning, and sending security out to hussle your @ss off the bridge! If it's for security purposes - it makes no sense whatsoever! Trucks which cd carry a lot more 'unsafe' stuff are allowed over the bridge, but a walking pedestrian!!???? Yes, middle aged Canadian women carrying knapsacks and tripods are very scary indeed!! *LOL*