Overall, the pickin's are kinda slim for hobby shops that specialize in model railroads - not to say that there aren't some in the Bay Area, but nothing I would label "must see". On the other hand, there are lots of publicly accessible model railroad layouts (though as I check their websites, the ones I like are not open to the public until later in the spring) and some 'real' 1 to 1 scale set ups. There's also a live steam layout in Tilden Park, just east of Berkeley, which has 2.5, 2.5, 4.75 and 7.5 inch gauge trackage (www.goldengatels.org) - some of which you can ride on. I think they are only open on Sundays. I also second the Sacramento RR museum and the electric traction at Suisun City (not as far from SF as Sacto) suggestions. One other suggestion is the Niles Canyon Railway, which runs between Fremont and Sunol (southern end of SF Bay - www.ncry.org). If you are going to be in Napa, you could ride the wine train (www.winetrain.com) - pulled by a couple of vintage Alco FA's
