Which way are you coming from Casper? Down through Rawlins then to I-80 or through Medicine Bow & Hwy 30?
For really good mexican food, stop in Rawlins at the Lariat or in Sinclair at Su Casa. (I prefer Su Casa, my MIL prefers Lariat). You could sidetrack off the interstate to Saratoga & eat at the Wolf Hotel. The deep fried mushrooms, salad bar, & steak or prime-rib are always good.
Search the board for Laramie & you will see we have a variety of local places that are pretty good.
I'm not very familiar with Steamboat, but we had breakfast at one place that was downtown & the pancakes were pretty good. It's a small mountain town, so you may have to drive around & pick something. As for Denver, there are a ton of recs on the mountain states board, just do a search, then follow up with any questions.