No, the EPA doesn't care whether the system is leaking or not, doesn't require you to fix, and doesn't prevent you from topping up a system which leaks. There may be tighter local restrictions in place, and I wouldn't be surprised if So. Cal. was one of those places.
The price sounds awful high to me, but I haven't paid for a/c service in the last 10 years or so. And that's only for a pound and a half of R-12, less than half a full charge.