I wish I would have taken a picture of the signs, but didn't think to since I was just passing by while traveling. I did have to wait about 10 min for one of the ICE owners to come back. It was on older couple, but did politely explain that these were our only "gas station" within a 50-100 mile radius.
Unfortunately, I think its just a matter of people not realizing that fact, and just assume its for local residents to charge up while they're getting groceries. Given that fact and that the grocery store was very busy (cars were constantly swarming, trying to find a parking spot), I can see why the locals park in these spots if open.
Since I'm not from there, I have no idea if the busy day was due to the holiday, or was a typical weekend. If there latter, this is poor planning by Tesla to choose that location. In that case, the only way I could see deterring this behavior is putting up the cones as someone suggested, or signs that threaten to be towed.