Ah, yes! The infamous California ground squirrel. IMO, the best control would be some nice big snakes. Something non-poisonous, of course, like some gopher snakes. They won't bother you at all, but they'll make short work of those rodents!
I invite snakes to my yard. At present, I have 3 large garter snakes, each about 3 ft long. One is black with red stripes, and the other 2 are olive green with yellow stripes. They do good work in my yard. I would also welcome any other snakes that chose to take up residence here, except for poisonous ones.
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams