For options in the city, Los Colibris was the most upscale restaurant that specializes in Mexican food (that I've been to). The service was excellent and patiently explained everything to us as we wrestled through the menu to figure out what we wanted. Our server was so good that she remembered a member of our party from his previous visits with them! The space is very dimly lit and was loud when the space filled up later in the night.
Food-wise, we ordered a bunch of items and shared them around the table. A stand out of the night was the Chiles en Nogada and the Empanadas. Both were favorites around the table. Yes, the price point is definitely higher than other Mexican restaurants ($11.50 for guacamole?) but you are definitely paying for the location, atmosphere and service also.