I've been here twice and I would say: mixed bag. Definitely go if you're in Cleveland and looking for a hip place that serves interesting food. Don't let the really negative reviews keep you away. It's worth trying, and there are some real high points. But don't let all of the high ratings on Yelp lull you into the sense that this will be without-a-doubt a great evening.
The vibe: it's hip and cool. Downstairs is definitely hipper and cooler than upstairs. Eat at the bar if you can.
The drinks: margaritas are excellent. Momocho's serves Mexican beers, which is what you'd expect from a Mexican restaurant, right? The beer they serve, though, isn't all that. The beer list is okay but not memorable.
The food: overall, very good. Try the smoked gouda dumplings. Delicious! The salsa is pretty good. The guacamole is really really good. I ordered the tuna tacos and was pleased -- not blown away. The tuna was well-prepared and the sauces were tasty.It just didn't knock my socks off.
The service: the people who work here are very accommodating, but they also seem understaffed. Our waiter forgot our appetizer (boo!) but gave us a free round of drinks to make up for it (yay!). We showed up earlier than our rezzies (bad on us) but the host seated us early (pretty amazing).
I'd definitely go again, with lowered expectations.