CanadianFlyer: Directions to parking lot closest and most easily accessible to cable cars:

From San Jose it's about a 50-60 minute drive depending on traffic and how leaden your foot is. Take 101 north to the 4th Street exit - the last exit in SF. Turn right onto 4th Street. Take 4th 1 block south to Brannan. R on Brannan 2 blocks west to 6th Street. R on 6th Street 5 blocks (I think) north to Mission. Turn R on Mission and look for the 5th and Mission garage. It's a big, public lot that's about a block long. Park there.

Find the corner of 5th and Mission (across from the new Sont Metreon shopping center) and walk 1 block north to Market Street. The cable car turnaround will be across Market Street to your right.

I suggest you leave quite early as there can be very long lines to take the cable car as the day progresses. Be sure to allow 2-3 hours for your cable car adventure, and try to get on the Powell and Hyde line if you can - it's the most scenic of the two lines that depart from the turnaround at 5th and Market.

In my opinion, the cable car barn, which is midway on the ride from Market Street to the other end of the line, is a must if you have time. It has the guts of the cable car system, and there's a little museum in the barn that explains how the cable cars work, a bit about their history, and how the system was built and then restored in the '80s.

A walk through the Metreon is also fun.

I can recommend quite good dim sum places within walking distance if you enjoy dim sum. In addition, there is a terrific Farmer's Market - often rated the best in the country - not too far away, if you enjoy that sort of thing.

Half a day in San Francisco? Not enough time! But it will definitely wet your appetite for another visit.

If you would like company and I am around, I would be glad to join you for a mini-FT get together for either of the above. In any case, enjoy your visit.