Colin wonders about public transport in California, which I must say is much better than the public transport I m used to in Canberra. Colin, to get to San Francisco, jump on the VTA light rail and head to the Castro Street (Mountain View) station. There, jump across to the Caltrain station, which will take you the rest of the way to San Francisco. I would think without having done it that you should allow about 45 minutes for the journey.
Here is the Caltrain trip planner for that journey… $7 seems pretty fair to me. I don’t really believe the two hour estimate that it gives there, but I guess it might be right.