If you are really serious about taking mushrooms, and not a total moron, you might want to read up a little bit on picking wild mushrooms. They Bay Area, and also some close by areas are abundan in wild magic mushrooms.
Google shrooms and northern cali shrooms, you'll find something.
www.shroomery.org
www.magic-mushrooms.net
Those are two great websites with plenty of info on shrooms. erowid.com also has tons of info.