I wouldn't call it 'authentic'. My favorite for that is Los Dos Molinos, but Abuelo's is my favorite of the chain Mexican restaurants. My favorite is the Nogales which is basically two burros, one chicken and one shredded beef, with different sauces on each.
You should order: Papas con Chile as your side dish. YUM. Also, you can have two fried eggs added on top of your enchiladas, burros, whatever. I love that and not many places offer it.