I’ll take your blanket assumption that most Mexicans work in gardening, construction, farms and restaurants. I make much more than many of these types of salaries and find it harder to afford shopping at Costco.
My point was that the number of people around me speaking spanish and other languages was quite unusual in my city. My wife noticed the same thing. In this area I think the numbers have increased dramatically and I can only assume they are coming here illegally. I assume this because our true ‘legal’ immigration system has not changed to allow a mass influx of non english speaking people to flood into my state.
Costco has actually great prices if you need quantity. Most Mexicans have large families so it makes sense financially for them to shop there.