Being right by UCSF, it takes me about 20 minutes to pick someone up from SFO and 45-60 minutes to pick someone up from Oakland. As a host, I would hope you were flying into SFO.
If you don't mind waiting 15-20 minutes for the airport shuttle to Bart, wait 10 minutes to take the Bart, which will take 40 minutes or so to get into the UCSF area. It will easily take you an hour and a half to get to your hotel or host's house if you're doing public transportation. I've done it several times and hated every minute of it. I used to just get off of Bart in the Sunset, which took forever. Then I tried the N Judah, which takes just as long and is extremely crowded.
Some people on here mention that it's no big deal which is fine. I must have a low tolerance for constant waiting and transfers. It would just irritate me.