If you can't make it to the polls on Election Day or you would prefer to vote early, you can do so either by mail or in person, and no excuse is required.
To vote by mail, request an absentee ballot by October 30, 2012. Returned absentee ballots need to be received by 8:00 p.m. on Election Day.
Apply to vote by mail or become a permanent vote-by-mail voter here.
Get more information from California's Secretary of State.