One of the things I would recommend doing in Oaxaca is to take a cooking class. I took one with Susana Trilling at Seasons of My Heart last time, and this time my spouse and I took one with Pilar Cabrera. Both of the classes were excellent and both of them take the class to the market to get to know the food you are going to cook and the people who grow it.
Pilar's class meets at her restaurant in el centro de Oaxaca called Las Ollas, and from there proceeds to the market, and then to her house for the food preparation and the meal.
We made a quesadilla appetizer filled with squash blossoms, thinly sliced red onions, fresh epazote, and fresh Oaxacan cheese (which is wild to find in the market because it is all rolled up in a ball that resembles a ball of yarn, and the cheese is unwound from the ball to cook with it). The end result was outstanding, but the truth is that we have squash blossoms a tiny fraction of the year and reproducing this at home is going to be an uncommon event. The best part was that while we bought the fresh masa from the market, we learned the consistency with which to make the masa in order to have the tortillas come out right and we cooked them. When we got home we found out two things--our local Mexican groceria has fresh masa, and we are not too bad at making it ourselves from masa harina. We bought both a ceramic and a metal comal (the surface on which you cook the tortillas) so we have the ability to make them the traditional way.
The Sopa de Lima was the second course. Limas are not widely available in Iowa (they are somewhere between a lime and an orange), but it may be possible to substitute. The soup is delicious and light. We also had cochinita pibil, a marinated pork dish that is cooked in banana leaves and also quite delicious. The entire experience was fun, enough hands on to learn something, and to top it off, there was a mescal tasting to round out the afternoon. Since we have been home we have used the skills that we learned in this class, which is a testament to the quality of the teacher.