RT13: From the looks of your post count, you're pretty new here, so I should ask you to pardon the biting sarcasm in the above posts, mine included. I really don't know much about CA restrictions, so I honestly can't help too much.
I will add, however, that the M1A is a nice rifle. I wish I owned one myself. However, I sort of doubt that it's going to come in under your $500 limit.
You didn't mention the application for this rifle (target shooting, hunting, defense, etc.) If you're looking for a self-defense weapon though, have you considered a good shotgun? It would easily fit your budget. It is the best of equilizers in close-quarter situations, and it can be a pretty effective long range gun with the right slugs. Not to mention the fact that it's still a relatively PC long gun (if there is such an animal) in the large scheme of things. For $500, you could build a really nice combat shotgun and still have some change for ammo. With a short rifle-sighted deer barrel, you'd also have a good gun for survival/hunting in addition to defense.
Just a thought... I know you might have your heart set on a nice rifle instead. But it sounds like those are getting scarce in Kalifornia.
If saands' advice on the SKS bears out with your local dealer, that's what I'd get--no doubt. Pick up a copy of Shotgun News and look for SKS deals. A few companies are still selling the Romanians for around $200-$250. 7.62x39 ammo is cheap and plentiful, and the SKS ain't a bad hunting rifle for a survival situation. Lots of folks around these parts use them for deer hunting.
As long as its not Full Auto, you can own it. 
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