Hi Matt - I'm in SoCal at the moment doing exactly the same thing - I'm flying out of Long Beach. There are a lot of firms here - I'm with Pacific Air who I've been happy with. If you do a search in the North American forum, I asked the exact same question about good fields and got some great responses, some of which I've visited already and some I plan to do in the next couple of weeks.
I considered Fly Corona, and the guys there were hugely helpful. I have actually flown into there as well and it's a great small airfield, but I actually like the busy-ness of a bigger field where you have to be on top of the R/T and there are other options in case your plane goes tech (actually happened to me today) and/or the weather is not great - although inland (as Corona is) tends to be a bit better than on the coast. In the end chose LB as it's a bigger city and for me, I wanted there to be something to do other than flying and Corona as a town, seemed a bit small for me.
If you are interested I am writing a blog on my experience - you can take a look at this link
Learning to fly from Day 1
My advice - do it - you won't regret it.