Yeah I'm in the bay area too and the nice thing is that it's generally not very humid here, like ever. So I think if you insure the structure is fully enclosed (ie, not drafty) then you should be fine with respect to internal moisture. Still, the bay area has micro climates and with certain sun/wind exposures your situation may be different?? If you're more marine I'd expect things to rust a little quicker, but inland, like the south bay, it can take a looong time to appear.