There's really only two ways to get to his office on public transit-
The 22 (which can be picked up at 16th & Mission BART, Church & Market or connects with many other lines, including the 9 from SOMA) to 22nd & Pennsylvania. Walk one block down Pennsylvania to the corner of Mariposa and you're there.
Or the K/T line to Mariposa, 3 or so blocks under the highway to the corner of Pennsylvania.
Well, i guess you could take CalTrain too, but that hill's a bitch...