This is a restaurant open only Thursday through Saturday evenings, housed in Sweet Pea and Petunia's, a casual restaurant on Rt 7 in Great Barrington (directly across from McDonald's). It is run by workers of the main restaurant who decorate the dining space with Mexican folk art and serve a completely different menu.
We had the following: tamales (Veracruz style steamed in banana leaves), meatballs in a chipotle sauce, and a carnitas torta. Appetizers are inexpensive and main courses are priced around $11-12.00. We found everything to be delicious - authentically flavored, prepared with care, and fresh. They are also now serving beer and margaritas, and the margaritas were quite good.
I'd like to return to try other items on the menu - they have different kinds of mole, enchiladas, chiles rellenos, carne asada, barbacoa de chivo (goat), even chapulines (grasshoppers, which are served deep fried).
The only other place I know in the southern Berkshires specializing in Mexican food is Xicohcentatls, not far away, but Mexican Nite has more authentically flavored Mexican food. I recommend giving it a try; the service is also friendly and hospitable.