Let me start of by saying that it is rare for me to have a Disney trip WITHOUT La Cava del Tequila! It is my favorite bar on Disney property, and I think the margaritas are worth every penny. I really enjoy the blood orange and pomegranate margaritas, and my boyfriend (who doesn't care for tequila) gets the avocado one every time. The cucumber margarita is also really different and refreshing.
The atmosphere is great... the perfect place to cool down in the middle of summer, since it's inside, very dark and has A/C. The bar can get very crowded, but if you don't mind waiting, do so.
My one tiny complaint about this bar is the lack of food. I know when they first opened and up until a few years ago, they offered different food options. Now, it seems to be limited to just chips with queso, salsa or guac. I'd like to see more food options on the menu, even if they are simple bar, snacking options.