Hey treasure tales, I couldn't help but notice, that you say you "get permission for state beaches"? Since when are state of CA beaches not full open game? We hunt them all the time here (Monterey, Asilomar, Seacliff, Moss Landing, Marina, etc.. etc... etc...) in full view of anyone and everyone, for the last 30 yrs, and never have a problem. Yup, even in full view of rangers.
One time, a state archie just HAPPENED to bump into a md'r on Seacliff State beach. It was just a fluke chance that he was at that beach that day, to give some sort of interpretive lecture for the museum that's right there. He looked down on the beach, and saw a buddy of mine detecting. He came down and tried to tell him "you can't do that". They had a debate, and the archie eventually stormed off mad. So when this info. got on the Kinzli CA forum, a few people wondered if this applied to all state beaches, or if this guy was even right, to begin with. A few people were going to complain or inquire or something, while others thought "treat this as an isolated incident, lest we bring attention to ourselves. Ie.: no one has ever cared, why rock the boat?" As it turned out, a forumite had a high-ranking friend in the parks dept. He inquired of that friend. The friend wrote him a letter, that stated there are no prohibitions about detecting state beaches. I think it has to do with the distinction between state "beaches" vs state "parks". Yes, they're both in the state park's system, but one is a beach, and the other is a park.
Now I grant you, if you asked enough questions, and went higher up the ladder, someone ELSE in the bureaucracy may say they're all one-&-the-same park's oversight, and tell you "no". But besides that one incident, I've never heard of anything else again. So as far as all CA hunters I know, it is only state "parks" you might have to be "discreet" at, not beaches. And it's best to leave it that way. Because as I said, if you asked enough state people, someone might see it differently, and start enforcing something.