I'm not sure exactly what a "potrillo" is, but my work friends and I just call this place "The Two Ponies". This is by far my favorite Mexican food restaurant in the Denver area. There are at least two locations that I know of, but for some reason I find the food tastes a little better at the location on Holly and County Line in Highlands Ranch.
I have never had a bad meal here, but my favorite dish, which is actually an appetizer, is their Chili Rellanos Nachos. If you are with someone who doesn't like spice, or by yourself, this dish alone is enough to fill you up. I have had similar dishes elsewhere, but this one is absolute heaven! You can see in the picture that it is so good I had already dug in before I remembered to take a picture!
My second favorite dish is their Carnitas platter, which is fried pork served with rice, beans, and tortillas. This dish is only served Friday through Sunday however.
If you find yourself on the South-Western part of Denver, this restaurant is a must.
Web site: http://www.los2potrillos.com/