There's a place in Oakland, 1420 20th Street
The place is like a cooperative of all sorts of makers; like a maker's fair; plenty of welders, laser CNC and more, lots more.
Some Burning Man structures are being built there. The building (Bay) is in the middle of the block, sort of tucked-in; there's a driveway and some parking inside.
In Daly City, Gomez Iron Works on Hillside close to San Pedro Road; they do mainly gates.
Out in Dublin/Pleasanton, International Union of Carpenters; lots of union members need hours of practice on welding to get certified and bet they would be more than willing to put a cubi-sh piece of steel together just to have more hours; doesn't hurt to ask...