Ending sentences with a preposition, y'all . . .

Rumpus correspondent Top Dog (a.k.a. "Queen of the East") sends in this joke:

A Southern lady sees a vacationing society lady from the Northeast. The Southern lady is gregarious: "Where y'all from?" Society lady is put off: "I'm from a place where they don't end sentences with a preposition." Southern lady smiles, nods her head: "Beg your pardon. Where y'all from, bitch?"