Search the San Francisco topic as a while ago someone posted a route down 19th St. The turn off 101 was just after you crossed the GG bridge. That route did not involve Van Ness (101 through SF)and put you back on the 101 freeway in San Bruno just north of the airport. When I was stationed in Marin County I took that route to the airport fairly frequently but that was in the very early 70's.
We were in that area just a last weekend and Van Ness is not too bad depending on the time of day. Lots of traffic lights but not too bad. We went through there just after noon. Stay in the right lane and follow the signs to 101 South and Oakland. Stay right to go south on 101 or left to take the Bay Bridge to Oakland (not recommended).