oh blue lady,
when the moon fills its belly
there is a rumble that aches

oh blue lady,
when the lone light shines upon you
the string bass beat chords

oh blue lady,
your lips part and I fall
through your caverns

oh blue lady blue.

a website listing of Blues clubs in SF and Oakland from the SF Blues Festival site just in case you need a blues fix before the festival:
http://www.sfblues.com/clubs/

Take your pick. I usually stay away from Friday and Saturday nights. Fridays/Saturdays in general tend to be more crowded and usually cost more if there's a big name. I tend to prefer the off days, when there's little to no cover fee and the blues is just as good.

In particular, ones that caught my eye (I've actually never been to any of them):

Boom Boom Room
1601 Fillmore/Geary, S.F., 415/673-8000:
Website: http://www.boomboomblues.com/
A great club with a lot of flavor and history. In the old historic section of Fillmore. Always good shows, good vibes

--Filmore the traditional center for jazz and blues in sf

Saloon
1232 Grant at Columbus, S.F., 415/989-7666:

Always good, tough blues here seven nights a week. Many of the established regional stars have gotten their starts here. Plenty of atmosphere, no jive, real deal.

--tough blues, sounds like something hearty for the soul to chew on

Lou's
300 Jefferson (Fisherman's Wharf), 415-771-5687:

Blues 7 nights a week; 2 to 3 bands per evening. Tommy Castro got his big start here.

--2 to 3 bands per evening usually gives a nice range of blues music


Eli's
3629 Martin Luther King, Oakland, 510/655-6661:

Home of the West Coast Blues! All the greats have appeared here. Blues seven nights a week. Pool table, barbeque, memorabilia, and tough Oakland blues. Worth a visit.

---When Blues makes a home here, you have to go. Oakland has a long history of Blues clubs, particularly in West Oakland, as part of the African American migration to the bay area, many of them workers on the ship yards during WWII. One of the ol' timers explained that Oakland was the Harlem of the west coast. This was THE place to be.

Bluesville
Jack London Square
131 Broadway at Second St., Oakland, 510/893-6215:
Website:http://www.bluesville-online.com

Jack London Square blues nitespot featuring blues seven nights a week, including Sunday jam, 5 p.m.. Dancing. Regional and national acts.

---Jack London is one of those developed areas. But you can't beat a short walk to the jazz spot Yoshi's, along with Kimball's Carnival, really building the Jack London Area as a real music district.