To unlock these cars, you have to progress through career mode in San Diego.

Car	How to unlock
Chevy 57 Bel Air	Beat City Tournament/57 Bel Air.
Chrysler 300C Dub Edition	Beat Balboa Tournament/300C Dub Edition.
Class C Vechicles	Progress in Career mode.
Hotmatch Chuevto	Beat Phil in Career mode.
Lexus IS300	Beat City Tournament/IS300.
Mercedes Benz SL500 AMG Dub Edition	Beat San Diego Dub Tournament/SL500 AMG.