I managed to get a "deal" on my mustang survival deluxe model at Fred hall two years ago at turners (guy threw in a rearm kit), I normally wear it since I don't notice it right off the bat, the one I got is manual so no worries about it inflating on it's own (good and bad). Castaic lagoon they don't care if you wear it as long as you have a pfd near you. Now the baywatch rejects at Hansen dam, that's another story!
I seem to think all the lifeguards there are pissed off cuz they have to work at this 9 acre cement hole that's only 14ft deep, ANYONE who gets on the water, they are practically yelling at to get their pfd on. I used to have a Stearn fanny pack one and had checked with them before I went in, they checked it out and said yeah your good to go. About a year or two later they are having some sort of training and there's like 40 of them there, "mr power trip" starts yelling at me where's your pfd, right here and I lifted up the pack, he keeps yelling at me then demands I get off the water, yelled back at him come get me!
Later the female guard on duty drives over to where I'm at and she tells me to get it on, I end up having to go to her and show her what I have. Mr powertrip gets on the radio and tells her hold that guy right there (yeah like he can do anything to me) she tells him he's good to go he does have a pfd what he was lifting up to show you is a fanny pack one. This story can go on forever but basically some places enforce wearing it some don't.