There is also the matter of having the property owner's permission. Isn't there an issue with stashing a cache on someone's property without their permission (i.e. trespassing)? Or removing/modifying city property or a business's property without their permission or knowledge (as in replacing the city or business's parking block with the other one)? I would think a property owner wouldn't be happy to discover you "snooping" (for lack of a better word) around on their property. I would think a city LEO would be less than understanding to discover you removing city property (assuming the parking block is in a city parking area). Likewise with a security guard for a business if it happens to be a business's parking lot.

I may be misunderstanding exactly what you have in mind or how you plan to do it. I certainly don't want to take this into forbidden territory, so I would definitely suggest having the property owner's permission to stash a cache or make mods to their property to conceal the stash.