The home owners should get 2 big barking dogs to scare off the illegals....I, myself, would feel tempted to hide and pretend no one was at home and take care of them my self.....
My dear Brother lives in Sierra Vista..AZ, and he has two large German Shepards that have been thru K-9 training. I promise you, he can sleep with his doors unlocked knowing his "boys" are always alert :)
sw