Just one quibble with a quote of yours:
They would eat every bit of food in their house and if water was off, they would take water out of the storage tank of potties and out of the hot water heater.
If we take this article's survey at face value, less than 1 in 8 of those who even bothered to take the survey, even admit to prepping. Personally, I think the number is even less when taken against the entire population. So, do you really think those neighbors of yours have the common sense God gave a shovel, to use the toilet tank/water heater as an emergency water source?
Here, I would say yes because we get every hurricane that comes through Galveston. Houston TV stations start telling people in early spring about how to find water in their houses. My area is upper middle class so I think they would use those sources. This is also a big church town. Most people here are going to be unwilling zombies but three days after no water, you and I know what happens. It's water or die - that turns one into a zombie seeking water, not brains to eat as zombies usually do.
We can ruminate about what will happen, using our knowledge of people, but if we are faced with collapse, we will have to be on guard from the beginning of it. My safety measures will be activated to the max, then I'll be ready for whatever happens and I take no prisoners.
To my knowledge, there are no preppers anywhere close to me but that may be because I don't tell anyone I am one. To everyone, I'm just a little old widowed lady who mostly stays in her house and they don't know anything about me. One banker lady across the street from me, knows my name and we have talked, have a good relationship, but she doesn't know I am a dreaded prepper. My preps aren't out in sight so even if someone came in, they wouldn't see them.
I hope I only have hurricanes to deal with and that you don't have anything happen in your area.