I really like Tapacubo. It has a nice atmosphere with a large bar in the middle, comfortable booths around the walls, a nice patio on one side and pool on the other (part of the attached Graduate Tempe hotel).
I have been twice now and had the guacamole and chips both times. The guac is delicious and they give an ample amount. The chips are fine, not great but who cares since the guacamole is so good. The chicken street tacos are amazingly good. In fact, they would be perfect were it not for the very average corn tortillas that seem like you could buy in a grocery store.
There is a small yet decent beer selection, thankfully not just a bunch of Mexican beers. When you get a beer on tap, they are served in plastic cups - kind of weird but priced pretty well so who cares.
If you don't want tacos, tortas or a few appetizer-like shared plates, this is not the place for you. The menu is quite limited, but that means the food they do offer is done well in this case. I'd recommend it - much better and unique than most hotel restaurants.