When I moved to Kansas from Texas, I had never heard of a Sancho. I don't care for them.
You tend to only find sanchos here in "Mexican" restaurants run by Anglos - the kind of places that do not serve menudo, barbacoa, lengua, tortas, and wouldn't dream of putting a taco on a fresh corn tortilla. Places like Taco (gag) Tico, Jim Kelly's Viva el Taco, and Little El Gringo. Places where they put melted Velveeta on all their "authentic" and non-spicy Mexican food.