Well you could try Metro PCS
Its a cheap company but you also get unlimited minutes for like $35 a month
They have service here in LA but im not sure if it goes all the way down to San Diego
VERIZON...I have AT&T now and like it before I had Verizon it was good with reception cost can be weird so make sure you work things out good with them. BUT they have a large selection of phones and plans including pay as you go and child phones
Steer clear of Verizon. They rip you off big time. Charging you for stuff they tell you there will be no charge for, surprise bills, end they just keep ripping you off and they threaten your credit report if you don't pay it. They get you locked in. Personally I've had much better experience with AT&T.