Actually, I'm just starting to look for preschools, too, though I live on another side of town. The JCA has a very good reputation, and the director has a very cool vibe and her philosophy seems to be in line with the things you've mentioned. I have also heard really good things about Seaside Playgarden (Waldorf-inspired) at the beach. http://www.jaxwaldorf.org/
It looks awesome, but it's too far for us. I'm not really familiar with preschools in Riverside. I have found that most preschools seem to be church-based. Good luck, and please post when you find something, as I'd love to hear about it.
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