Irish sessions on Sunday and Tuesday at The Plough and Stars in SF (not to be confused with The Starry Plough in Berkeley!)

As for stores -- there's Lark in the Morning (instruments from all over the world, plus instruction books) in the Cannery at Fisherman's Wharf, where you should go anyway for the fresh crab.

Best record store in the area is Down Home Music in El Cerrito (next to Berkeley).

You could also PM Mudcatters radriano and Dave Swan to find out what they know.

Cheers,
Michael