Two families in our neighborhood drove from Oakland to Alameda to have their children in preschool at Peter Pan. I visited the school and it was very sweet. It's an excellent program. Peter Pan is a co-op, so tuition is low, but parent commitment is high.
One thing- my son was in a preschool in Oakland, Inch By Inch, that was home-based, meaning that it was licensed as a family daycare but had a really excellent play-based program with lots of messy art, music, and movement. The children learned all of the things they would learn at a standard preschool- how to pay attention at circle time, how to share, how to transition from one activity to another. There were pre-K activities, and all of the children left knowing their colors, their numbers, the alphabet, and how to write their names. They also did gardening, capoiera, Spanish, and drumming. The adult to children ratio was excellent- 1:6.
You might want to check into that option when the time comes, especially if you have trouble getting into a preschool of your choice- there are some daycare providers who run excellent programs with lots of enrichment activities, no tv, and organic meals. There are day care providers who are well educated in early childhood theory and love their work. It's definitely worth a look.
Our experience was that the preschools we applied to simply had an application period and a lottery, in December I think, for the following fall. Not to worry you, but we got in nowhere. We were way down on every waiting list and fell just short of getting our first choice. So we enrolled our son in preschool at Inch By Inch, where he was already in the toddler program, and never regretted it. It's a great program.
Don't worry now- your baby is only six months. It's good though that you're looking into the programs available in your area. I've heard SavySource is a good place to look into preschools on line. Good luck! Enjoy that baby!