Definitely do the tourist sightseeing... Pier 39, Coit Tower, cable cars, etc. Alcatraz if you have time. Angel Island if you have lots more time.

Also the SF Fire Museum is pretty neat:
http://www.sffiremuseum.org/

The SF Maritime Museum and Park:
http://www.nps.gov/safr/

And there is the Presidio (now run by the NPS):
http://www.nps.gov/prsf/

And of course the GGNRA:
http://www.nps.gov/goga/

There is an REI in San Francisco, too:
http://www.rei.com/stores/sanfrancisco/index.html

You're probably not going to have a vehicle, but the cabs and MUNI buses cover the city pretty well. If you do have a vehicle, getting around isn't too bad, but parking can be a pain. Also watch out for the red light cameras.

Have a safe & fun trip! <img src="/images/graemlins/smile.gif" alt="" />