The San Joaquin County Office of Education periodically offers Spanish lessons to adults, and another round is coming up from March 6 to May 8. That’s Wednesdays from 4:30 p.m. to 7:30 p.m. The lessons are for all levels of proficiency.
I took one of these programs in 2011. I learned a lot and it was fun, too.
Details, contact information, plus the registration form are here.