The town of Juchitan, on the isthmus of Oaxaca, is most famous for it's strong women and hot climate. It's a fascinating place for many reasons.
On the main zocolo, you'll find Casagrande restaurant. It's a fine old colonial building that could be a nasty tourist trap but instead it's a very good restaurant serving regional food.
Especially nice was the taco amuse bouche that was shrimp tossed with onions and poblano strips and topped with some guacamole.