@ MinisterAmos: "...the wall surrounding the property is only about 2-3 feet tall...
I'm relatively short but I would find 2-3 feet to high to step over for almost anyone. Why would they even put a wall if they just want to shut off entry to automobiles? Perhaps they were being cheap with a low wall but it seems that they want to block pedestrian access to the parking lot.
Have there been any instances of pamphleteering the cars? I know that putting apostate literature at JW home's doors occurs every once in a while. An alarm, even if it covers the parking lot, would not do much to prevent pamphleteering which could take only a couple of minutes.
But I'm just brainstorming.