<< BART includes the streetcar system, which is very good, too. I have used it often when in SF. >>
BART is separate from MUNI (the "streetcar system"). Unless you've driven around in S.F. before, I would recommend taking public transportation. Otherwise, if you've driven around in the city and feel comfortable with it, I would just drive. It'll get you around faster than any public transportation. However, you'll be paying a little for parking.