Rudi - The bus numbers have changed. 7B became 292 and 7F is now the KX. I took the KX this last weekend and it's great because it hops on the freeway and gets off in the city going down Mission (parallels Market and one block away). It took about 1/2 hour and costs $3.

Caltrain is ok but it doesnt really let you off walking distance to Financial District.