The CSUs in southern California vary all over the place in selectivity. With a 3.8 HS GPA and all a-g course work complete, you do not even need any test scores for admission to non-impacted majors at non-impacted campuses like Bakersfield, Channel Islands, or Dominguez Hills.
However, San Luis Obispo and San Diego are impacted for all majors and more selective, so a high SAT or ACT score is desirable to have a good chance of admission.
Read about CSU impaction at http://www.calstate.edu/sas/impactioninfo.shtml .