I hunt any and every park I come to. Barring a sign that says "no metal detectors" or barring an obvious historic sensitive monument.
But if you are skittish that some places might have a rule, look it up for yourself. Do not walk in asking some desk-bound park person: "Hi, can I metal detect?". Lest you find yourself the latest victim of this: "Sometimes no one cares UNTIL you ask". That is to say, there's been lots of parks, beaches, school-yards, etc... that were never a problem, and no actual rule existed that truly said "no metal detectors". But lo & behold, someone takes it upon themselves to go ask, and finds an arbitrary whimsical "no". Then the danger is, that that same person (who perhaps never gave it a moment's thought before your "pressing question"), will now start booting others.
So if you're skittish, look it up for yourself. Park rules, city ordinances, codes, etc.... are no secret. They can be looked up on-line for even small cities nowadays.
