It's really hard for me to review Mexican restaurants in New England, because I have yet to encounter one that tastes even remotely authentic. Tortilla Flat is arguably the best "mainstream" Mexican-style restaurant in the area (although I haven't tried the little tacquerias that tend to come and go), but it still doesn't measure up to a decent Mexican restaurant in Colorado, California, or Arizona (hence the rating of "average").
Upon arriving at Tortilla Flat, you'll be ushered into one of a number of small rooms decorated with antique stoves, colorful serapes (Mexican shawls), and southwestern-inspired paintings. The ceilings are low and the walls are covered in barn boards or logs-and-mortar. It's definitely different than your average New England restaurant setting.
When we arrived for our last visit to Tortilla Flat, we were greeted warmly and seated quickly. Within moments, we had a basket of tortilla chips and mild salsa. (I would have liked a selection of salsas for different flavors and spicing levels, but this IS New England...) We continued to have excellent, attentive service during our entire meal.
While we were waiting for our main dishes, we tackled a plate of "loaded" nachos. This dish consisted of tortilla chips topped with ground beef and cheese along with two small cups of guacamole and sour cream. The ground beef was not spiced enough for my taste; it was definitely bland. At least the cheese was grated queso blanco or something of that nature instead of the orange liquid that passes as nacho cheese in low-end food outlets.
I like the fact that Tortilla Flat's menu contains chile rellenos and tamales, two dishes that are often left off of the most Americanized of menus. I had a pork tamale and it was reasonably tasty. The guacamole I ordered on the side was extremely bland: I'm used to guacamole made tableside with a lot more lime and a generous helping of cilantro--this fell far short. While the lime may have been there (although I couldn't taste it), the cilantro was definitely absent.
My dining companion had a special, lime-marinated pork tenderloins in a chipotle pepper sauce (pork carnitas). I tasted it and the pork hadn't been marinated long enough to pick up sufficient lime flavor, so that the pepper sauce, while not being particularly spicy, still managed to overwhelm the taste of the pork.
The best dish of the evening was the empanada we ordered for dessert: a tortilla filled with cooked, sweetened apple chunks that was then deep-fried, served with ice cream and caramel sauce on the side.
The prices were reasonable and the quantities were generous. The tab for all of the above, including a glass of red wine, was $40 (to which we added the tip). Given the lack of truly excellent Mexican restaurants in the area, we will likely be back to Tortilla Flat, but I wish the food was more flavorful.