Check with the local community/junior colleges. They are the places that most of the EMT-1/Basic classes are offered. Some community colleges offer paramedic training, too. There are also private EMS schools across the county that offer EMT courses. I believe that if you're nationally registered (NREMT) as an EMT-Basic, you can easily get an EMT-1 cert in Calif. For the complete story, check out the Calif EMSA website at: www.emsa.cahwnet.gov for more info.
FYI, paramedic school takes some commitment. I've seen lots of people drop-out or not pass.
Erik, Calif EMT-P