As I mentioned in my seminal blog post, Ecuadorian Quinoa Chowder with Sweet Corn, if you want to create authentic cuisine, it's vitally important to find good ethnic supermarkets. Nothing against Hy-Vee, but I'm pretty sure they have to outsource the ingredients for their own Chinese buffet...
So where should you go if you want to find cactus (for when okra just isn't slimy enough) or tomatillos that don't look like turn-of-the-century English orphans? Well, Avanza Supermarket would probably be a good start.
When is the last time you saw that many tomatillos in the grocery store? Unless you grew up on a tomatillo farm/grocery store (which, according to Blogspot's overly specific user data, represents about half my readership - the other half are bots originating from former Soviet Bloc nations), I'm guessing it's been a while. The point I'm trying to make is that Avanza has a tremendous selection of (affordable) vaguely ethnic foods that seem to get neglected in most major grocery stores. I can appreciate an Old El Paso taco seasoning packet as much as the next guy, but your girlfriend's abuéla (five years of Spanish, people) may disagree.
Oh, and here's a wall of tortillas.
Much like the Great Wall of China, Avanza's famed Tortilla Wall can be seen from space.
In case I haven't made it clear, go to Avanza. Be adventurous and support a less well-known ethic supermarket. You can still go ahead and buy your Doritos at Hy-Vee if you're concerned about their financial solvency.
And, yes, Avanza does have Takis.