Growing up on Long Island (pronounced "Long Guyland") I'd see little "Curb Your Dog" signs on some lawns. In Portuguese, that's "Limite seu cachorro," according to Lingvanex. Seeing that in his native tongue might get the message across to your neighbor.

An old guy I worked with was pissed off at some dog that would piss on one of his bushes. One day he somehow added bare wire to the bush and electrified it and then watched with glee how the dog jumped and whelped and never returned. Such a scheme would not work on poop unless it's a long steady stream of diarrhea, and even then I'm not sure the electrical conductivity of diarrhea is anywhere near as high as urine, which, actually, has been characterized.