- There are many excellent taquerias in The Mission (la taqueria is a classic, I am partial to Buen Sabor on Valencia), but I've been going to El Falorito basically since I was a kid, probably the best burrito in the city
-City Lights Books is a classic bookstore to just hang out in, but Vesuvio right next door is a wonderful spot for a drink
-There's a new park in the Presidio that's fun to have a picnic at!
-Bottom of the Hill always has gigs happening, it's got a gig calendar up. 924 Gilman St if you're more into punk music but it's a BART and bus ride over into Berkeley (which you should also check out if you have time)
-A bit outside of SF as well, the Marin Headlands have some wonderful hiking, but you will need a car to get there, similarly Pacifica/Half Moon Bay have gorgeous views of the Pacific, but a car will be required
-You could spend hours in Golden Gate Park, I like starting at the De Young and then going from there. SFMOMA is a classic as well.