My informant is a 47 year old psychotherapist from Hermosillo, Sonora, in northern Mexico, who currently resides in Mexico City with his wife (my aunt) and two young sons. He told this joke at a family meal in Mexico, during a very long exchange of jokes among family members.

“Anda un vato de Nabojoa en el supermercado así gateando en el piso todo así *lowers down* y entonces anda en el super aqui y se encuentra con un vato de Guaymas, y que le dice “y que andas haciendo guey” “pos aqui buscando los precios mas bajos!”
Es regionalismo, la gente de Guaymas y Hermosillo se sienten superiores a los de Nabojoa.”
“Donde lo oiste?”
“En el estadio de beisbol, en un juego entre los Naranjeros de Hermosillo y los Mayos de Nabojoa.”

Translation:

“A dude from Nabojoa is at the supermarket like that crawling on the floor all like this” (lowers down) “and then he’s in the supermarket there and he finds himself with a dude from Guaymas, and who tells him ‘and what are you doing man’ ‘well I’m just here looking for the lowest prices!’ It’s regionalism, the people from Guaymas and Hermosillo feel like they’re superior to those from Nabojoa.”

“Where did you hear it?”

“In the baseball stadium, at a game between the Hermosillo Naranjeros and the Nabojoa Mayos.”

I have another take on this joke from my informant’s son, who knows a different version where the guy on the floor is just a son and the guy asking him what he’s doing is a mom instead. I think it makes sense that the younger boy knew this version because of what it has to do with being young and misunderstanding things. His father, on the other hand, associates the joke with a rivalry between his hometown and another Sonoran town, especially since he heard it at a baseball game between his hometown team and the opposing team. So while his son uses the joke to play on his identity as a young person and a son, his father uses it to play on his identity as a person from Hermosillo.