Whereabouts in Los Angeles? schools? parks? beaches? city land? county run places? state run places? fed. run places? You need to be a bit more specific on type places you intend to go.
To my knowledge, there is nothing off-limits down there (all parks, schools, beaches, etc... are ok). However, I've heard that some of the school yards are fenced off, with lots of ominous signs. But that's not per se for detectors, it's for any after school use (they got tired of being sued for people getting hurt on the monkey bars or whatever).
Get on the Kinzli forum. There's a lot of Los Angeles area hunters there, who'd have more info. To get the main page of the Kinzli forum, you'll need to become a member. But it's easy: just pick a name and a password
