First, you’ll want to go to Fiesta at 6200 Bellaire Blvd, Houston, TX 77081. It’s very close to your hotel. Go during the day. You could very well be the only native English speaker in a gigantic store; (and I mean even Texan English, much less the Queen’s.) This is the original location in a booming local chain. It’s an international store so you will find not only Latin foods, but a great variety. Budget at least an hour or more. It’s Foodie Heaven. As I hinted about above, it’s not a location I would normally send a tourist I was trying to impress, but it’s something I hope you’ll appreciate. It very much serves its constituency.
Wheat and corn tortillas(I can get wheat ones locally but they’re quite poor). I assume by “wheat” you mean what we call “flour”. My favorite are made by La Rancherita on Berry near Alamo Tamales. I have only found them at a downmarket shop called Food Town. If you can find those, I recommend them. As for corn, I have no preference. I prefer yellow corn to white and just look for the most pliable ones, (freshest), I can find. They keep forever so stock up. Pro tip: Like bread, the freshest ones will be shelved closest to the floor. They move them up over time.
Fresh poblano peppers Everywhere. If you like poblanos,you might also pick up some anchos, the dried version. Also keep forever and essential in so many things including real Texas chili. There’s lots of other dried chilis also.
Chipotle peppers in adobo sauce Wide variety available in multiple sizes, including rather smallish cans which I like. San Marcos brand is what I usually get, but I don’t notice much difference.
Cans of crushed tomatoes Cut, crushed, pureed, etc. You’ll have lots of choices.
Mexican oregano Look to the bulk bins for this. Throw it in a clean glass or plastic jar when you get home. I actually buy mine at a local spice shop called Flores on Airline. I drive halfway across town for it when I’m out. Love that stuff.
Velveeta, Rotel, Clam juice You know what you want there.
Salted anchovies (i.e. packed in salt rather than oil) Ditto
Canned San Marzano tomatoes Ditto.
You can get all of these things at pretty much any local grocery store. If you want a …well, let’s say a more “English-centric” option, go to HEB. It’s equally well provisioned.
I know you’ve been here many times before but nevertheless I hope you have a great trip.