I don't know if there's any regular places, but you gotta be able to hear some jazz in downtown SanMateo or Burlingame every once in awhile. I'll probably be playing soon at a cafe in downtown SM soon (just gave them my CD), but I don't do straight jazz. Check with KCSM's calendar. The live music scene here is severely lacking! Places are trying, but it's hard for them to get going because the permits/politics/regulations are a lot stricter and the evening scene has just evolved away from that sorta thing. IF you look hard enough there is music, but I usually just go to SF.

OH I just remembered - sometiems Cafe Borrone in Menlo Park has a dixieland jazz band, but it's certainly no speakeasy, and I don't know how regular the music happens.