I have a friend who lives in San Diego and he hires an exterminator every couple of months, and he still kills them inbetween...
He goes out and looks for them in the evenings and take matters into his own hands.
Another option is to go to Nevada, or someplace hillbilliyish and buy some GOOD Insecticide to spray your yard every week or so. OTC stuff just doesn't have the killing power like the industrial stuff
If that is not an option, I could probably fedex you some good insecticide I can get from one of the local farmers...