Magic man, "state parks" aside for the moment (since you direct your comments to city manager, so I would assume you're talking city parks), you say: "Better off checking, then getting a ticket or landing in jail." Can you cite any incidents of this happening, in city parks that are innocuous non-historic monument type places? I mean, for the average Joe Blow city park, not posted, can you please cite me any incidents of tickets or jail? My suspicion is that you can't. There are a few incidents floating around on some internet thread (the Houstan thing), but my response to that is, that 1) it will get thrown out (there was simply nothing suggesting a person should've known, if they were never warned, and it wasn't posted, and they weren't making a mess or being a nuisance). Or, 2) any incidents are so extremely rare, as to be ridiculous. I mean, if everyone reads of the Houstan incident (which, as I say, will just be thrown out anyways), and thinks this means they are in danger of tickets or jail, means you base your life on extreme exceptions, not on norms. That would be like hearing of a driver who got roughed up & jailed by overzealous cops, for a simple tail light infraction, and thinking "oh no! I better not drive anymore!" Or "maybe I need permission to drive now!" rather than see the situation for what it is: an exception that is a fluke.
There was a time, when ... on internet forums, someone would cite fears of jail or tickets, and I'd ask them the same thing: "Cite me an incident of such a thing". And EVERY time, none were forthcoming. Or if they could find something, it was guys night sneaking historic monuments, or persons who couldn't take a warning, etc... Now I do admit, a few odd stories circulate, but as I say, they are the extreme exception. I've detected at parks in any city I come to, and never "ask permission" Yet I've never had a ticket or jail (wow, imagine that). I don't consider myself any different than someone using the basketball hoops, jogging the track, or skipping stones on the pond there. Just as I wouldn't feel the need to ask "permission" to do those things, so to do I not consider detecting any different. If someone has an issue, they're welcome to come tell me. But the minute you or I start asking, is the minute you only caste aspursions on yourself, or the hobby, that it was so evil, that you had to ask. JMHO