If you're willing to drive about 15 (probably less) mins north, there is an Open Gym at the local community college in San Pablo which is open Mondays, from 7-10p. It's 3 dollars and in Contra Costa Community College (exit El Portal Drive). There is a lot of people there. About 12 courts and it's a first come first serve. It's wooden floor like high school gyms. And the players rank from Low A to Low D. Hope to see you there.
Whats the current price there? Open gyms around the area are probably the cheapest, but besides that there is GGBC, Bintang, and UBC within driving distances.