I've never been to Nicaragua but the food here is very similar to what I ate in Costa Rica, so I'm assuming it's quite authentic.
I'm in love with the ceviche at this place. It's so fresh and served with baked plantain chips (nice and light, not greasy/fried). They do shrimp ceviche, fish ceviche or a combo of both.
As mentioned by others, the combination plates are HUGE and cost $11-13. I can easily share with another girlfriend or it's good for one giant size man. Each meat dish comes with a few side dishes noted on the menu, but if you ask they will custom make your plate so you get whichever meat dish and whichever side dishes you prefer. The fried plantain is so tasty...mmm
I always go here with my boxing coach, who is Cuban and is friends with the owner. The staff and owner are always very friendly.
My only complaint is I wish they had some kind of lunch menu, as I find the main dishes are simply too huge for my smaller lunch appetite. But the ceviche can be nice lighter meal.