T.F.
Hi, my children have gone to/go to Horizon Hills Parenting Program.
http://www.conejo.tec.ca.us/parenting/Parenthome.htm
We've been pretty happy with it, but it's a Parent Co-op (play-based, developmental) and only half day (but very affordable.) So that won't work for you. Gosh I don't know what to recommend as far as preschools. There are so many and we've been pretty happy at HH. I have heard that children with your sons issues may not do well in other area preschools, simply because the teachers don't know how to handle it and may handle it inappropriately. You might want to check out Temple Etz Chaim and talk to the office (call up EVERY place) and ask to speak to the Director if you can and describe your situation and see if their place would be a good fit for your child. Many have websites so call and ask.
http://www.theneighborweb.com/ConejoValleyPreschools.html
But there is a program in Westlake Village that is supposed to help children who have attention difficulties. My friend (has an 8 yr old boy) is doing it now and sees improvement with her son. She's been driving to the SFV for years. It's pricey, but I think children are worth it. If it were my child, I would check it out.
http://www.brainbalancecenters.com/
HH hosts a wonderful Parent Talk & Teacher Talk series. Debbie Wilson of "S'cool Moves" will speak in April and it might be good for you to attend her talk. She had a daughter with severe delays (different situation from your child) but the therapies she used (after doing her own research - she was a reading specialist) did wonders for her daughter.
http://www.schoolmoves.com/
http://www.conejo.tec.ca.us/parenting/teachertalk.htm