SFO is not that far from downtown SF (unlike, say Denver) and with 3 of you I would absolutely suggest a cab. It may cost a bit more per person, but it will save your evening. That hour on Saturday may not be so busy and Super Shuttle will need to collect enough fares. Take the taxi... by the time you get there, get checked in and get ready to go out you will be still be on the decently front end of Saturday night and will get to enjoy the city. Worth a few dollars. (By the way, it is foggy and cold here these days so bring something to wear to stay warm with in the evening!!)