I am a HUGE fan of authentic Mexican food. The Monona Super Tienda is a gem of a find. They have a large fresh meat counter with tons of well trimmed specialty cuts of beef and pork (some chicken). If you are preparing that authentic Mexican recipe this place has your meat and their prices are much lower than Woodman's.
Now to the best part--The Taqueria. They have a small cook-to-order counter with assorted traditional meats and fillings for your fresh made taco, torta, or combo plate.
The food is the most authentic Mexican fare that I have found anywhere at any price level in the Madison area. They also have a good selection of well priced produce and groceries and yes--the avocados are always ripe and low priced!
They do have a small seating area with about 4 tables to eat at.