You should have a lot of Solenopsis invicta around you. Huge portions of Riverside has tons of those. I went all over Riverside and saw huge (1-3 foot tall) mounds all over, amongst Argentine ant areas.
If you get out of the city, Forelius pruinosus/mccooki remain active year round in most places. They are easy to get too, but most don't tend to fly...they bud out. I guess they do fly, but none of the ones I've seen do. They are a great ant species to keep though. Vastly easier just getting a queen (or queens) with some workers, as starting with just one queen is a lot harder than a lot of other queens in other species.
It also skipped most of Winter in southern California, so ant season should be a LOT earlier than elsewhere. Here in Irvine (Orange County), it got to 81 degrees today!
Edited by Vendayn, January 23 2015 - 8:10 PM.