Mexican breakfast at San Jalisco (20th and Van Ness)
And while you're in that neighborhood, get delicious coffee at Philz Coffee (24th and Van Ness). They have their own SF style you won't find in Seattle...
Friday or Sat night, goto a "show" the Audium (audium.org). It's a sound sculpture space that will take you back to the futurism of the 60s.
SF MOMA usually has good exhibits, but go on a weekday.
Get some drinks at the Gold Dust Lounge in Union Square. It's a really old dive bar with a gold rush era feel. When I went, there was a piano player and people getting super wasted and singing along.
The Academy of Sciences in Golden Gate park is really fun: planetarium, living roof, rainforest, aquariums, all encased in a modern, sustainable building.
And if you are at Golden Gate park on a Sunday afternoon, you should check out the roller skaters in the central north side of the park. They usually have a sound system set up and people practice their routines. Great people watching...
Oh, and definitely goto the beach!
Have fun!