I could probably count on the fingers of one hand the number of times that I have been to a Walmart back home. Yet whenever I take friends to Mérida we stop at the Walmart on Paseo Montejo. Years ago I read an article in the travel section of the newspaper in which the author wrote that a tourist to a foreign country should always visit a local supermarket.
Even though Walmart is U.S. chain, the differences between the supermarkets in Mexico and the U.S. are obvious. A visit always provides a lesson in the food culture of the country. We pass through the produce section, and I point out fruits and vegetables that you are not likely to see back in Ohio... the paddles of nopales (prickly pear cactii), tejocotes (a small fruit used in fruit punch), jícamas (a root vegetable) and chayote (another vegetable that grows on a vine), etc., etc.
I don't know about Walmarts in California or Texas, but I know that the stores in Ohio do not have a "tortillería"... a tortilla section.
The baked goods section is set up like a typical Mexican bakery. You take a tray and a pair of thongs and select the items you want. Then you take the tray to the counter where the clerk wraps your purchases, puts them in a paper bag and attaches the price.
Visitors from the U.S. are usually amazed to see that eggs and even cartons of milk are not kept in the refrigerated section.
And before someone mentions it, yes, a visit to a traditional marketplace is also a "must". We have gone through two small neighborhood markets here, and perhaps today we will visit the main municipal market. I have to say at this point that the one in our neighborhood of Santiago is a sorry excuse for a market. Very few of the stalls are occupied, and the place smells very badly.