West End Gun Club has been out of the Highpower game for a few years now, basically since I became a member to take advantage of it. This is a sort of master calendar with links to the various clubs:
http://www.socalhighpower.com/ From Cerritos both BRRC and the Santa Margarita Gun Club should be about the same distance, Castaic and Camp Pendelton respectively. The Santa Margarita Gun Club shoots on base so you have to pre register online before the match so you can enter the base but it's fairly easy and the facilities are large and nice. Burbank Rifle And Revolver Club has a smaller range with 5 firing points and pits at 200, 300 and 600 yards so you don't have to drag your gear all over the range for XTC. Their firing points are also covered with a mesh so you have a usable amount of shade. Also of note locally is the Los Angeles Rifle And Revolver Club which shoots Smallbore most weekends, also a nice covered range.
http://www.larrclub.org/