dweste, I am not sure why you are researching AR15s in California.
You missed that bus years ago.
Unless registered (that time has passed, BTW) , AR15s are essentially illegal in CA.
Have a look at calguns.net for more details on California law.
Sorry to be the bearer of bad news.
You have been misinformed on the legalities of AR-15. They are legal (not just the .22 version), and in fact quite a few stores have them on display and for sale.
Dweste,
I think you're making a good choice by going with a dedicated .22 instead of a conversion. I never really saw an advantage of taking a $1000+ rifle and adding a bunch of accessories, to end up with the functionality of a 10/22