I'm from Chihuahua and I can confirm this, burritos are really common over here, but not so much in other parts of Mexico.

Burritos are the food you will get when you're in a hurry. You are late or you simply don't want to cook? if you have some leftovers and flour tortillas then you have burritos! You're on the road and you want something inexpensive and ready to eat? Just look for the old lady selling burritos on the street.

American burritos are kind of different though, we don't usually mix beans with rice, lettuce, cream and all that stuff. Instead we use traditional dishes like chile colorado, picadillo, chicharron en salsa verde, discada, barbacoa or whatever we have on the fridge ;)