"Unless they live along the border and go back to Mexico to do their major shopping."

From what I have seen, shopping across the border in Mexico sucks unless you want souvenirs.

The Mexicans stream across to the Walmarts to stock up.

And guess what they buy the most of? Pampers. You see decrepit pickup trucks with cardboard stacked up 10 feet high heading back to Mexico. I guess that use it to build houses.

In Maine where I95 ends, Canadians are streaming across the border into a big Walmart.