“Pepper spray on the type sign you press into ground. Spray along the plastic edge. If it rains? Re-apply. I use FOX Lab spray. As do many PDs. Hot as hell.”
“Liberally coat the back of them with thick automotive / marine grease. I’ve worked with some black stuff that was weatherproof and very difficult to get off of your hands and clothing.”
i like those two ideas best ... but the two can be combined: get a pint bottle of inexpensive Cayenne pepper from Costco or the like, and mix it with a really nasty grease augmented with some nasty cutting oil ...
it worked really good when squirrels kept gnawing through the dumpoff line that runs from my rooftop evaporative cooler down the roof to spill over the side of the gutter ... prior to that, there was a whole squirrel convention gallivanting all over the roof in the early morning, but afterwards the squirrels abandoned my roof completely and never came back ...
i figure if that concoction is good enough to discourage squirrels, it could discourage sign thieves too ...
(poison ivy/oak extract should also work well ... get a bunch of the leaves and stems and macerate them in a small amount of vegetable oil and let sit a week ... btw, this is an extremely dangerous thing to do without proper disposable protective gear AND zen-like attention to decontamination without touching anything that isn’t disposed of ... everything that is used to make and apply this stuff should also be disposed)
I suspect the sign will stick to people for some time. May be extra enjoyment to add ground ghost peppers or habanero to the mix. LOL! Make 'em shake like Hillary!