Hey there - California is definitely much warmer than RI. However, like you said...the cost of living is not so great, especially in the cities (SF, LA, San Diego). There are ways to make it work though and the sun is always worth it!
I don't know of any live/work co-op places, but I'm sure you might find some online. Check out www.ic.org/. They have a pretty good listing and it looks like there are a lot of them out here.
As for artsy/green places, I would look into Berkeley, Fairfax, Santa Cruz, San Louis Obispo, Sebastapol. Those are still close enough to SF if you want to ever go to the city.
Hope that helps...
