Check out West End Gun Club out near Fontana. They run monthly matches, usually on a Sunday and they are starting to hold NRL22 matches.
http://www.socalprecisionforum.com/
James and a Henry kinda run the deal. Good group of guys.
I was planning on getting more involved with them but recently got sidelined with knee surgery.
I'm in LA too and shoot up at Angeles most Saturdays. I've kicked around the idea of getting a group of guys together and renting a private range there but I think the private range only goes out to 100
There are a few more clubs starting to get more involved with the PRS style but it's usually word of mouth.
Hit me up if you ever wanna shoot
Kyle