We use the BART train. It's awesome. It's the San Francisco BART train subway system. It has lines connecting to the Bay Area
THe lines are
Fremont-Daly City (WEEKDAYS AND SATURDAYS)
Fremont-Richmond
Dublin/Pleasanton-Daly City/Millbrae
Richmond-Millbrae (WEEKDAYS ONLY)
Richmond-Daly City (SATURDAY ONLY)
Pittsburg/Bay Point-SFO Airport
In San Francisco, there is a MUNI that travels to places BART doesn't travel to, so it travels through Embarcadero, Montgomery, Powell, Civic Center, and outside of the Transbay Tube