Carolina's is likely the most 'authentic' and delicious Chihuahuan-style food in the Valley, at least that I've come across. This is the style of Mexican food that I grew up eating, and although I love the whole spectrum, this type is my favorite due to its greasy-ness, inclination to corn tortillas, and beef ... lots n lots of beef.
Carolina's is certainly the bare-minimum of establishments. There is an order-counter, almost soup-nazi-esque as far as the intimidation factor goes, but the staff is extremely friendly and will help you customize your order. You then have to wait for your number to be called as you stare at your oozing tiny dixie cups of salsa in anticipation.
I always get the machaca burrito (holy smokes, my mouth is literally craving it now -- dammit, why did I write this so close to lunchtime?) with sides of rice and beans. I'm a bitchy critic when it comes to the latter, as the entire female familial line of P.'s can work out some magical rice and beans, yo ... and these compare favorably. I wish Carolina was in my family.
Oh, and they rock red Fanta as a soda option because they F'ING KNOW that the Mexis love their strawberry bubblegum flavored drinks. I can never pass up this option no matter how hard I want Dr Pepper or Sprite instead. Some sort of congenital condition, like its a vital fluid, that red Fanta.