My wife and I ate at Mirador on multiple occasions during our stay in Atenas. Each visit greeted us with some terrific food! In addition the service is top-notch and the view is breath-taking looking out the back of the restaurant.
The restaurant is a very open-air setup, so it always seemed comfortable and the overall architecture/layout of the place makes it seem like a huge place!
My wife and I (and kids) enjoyed many of their dishes - breaded fajitas, arroz con camorones, arroz con pollo, fish with garlic sauce and some of the steaks were some of our favorites!
The fish is always very fresh and cooked just perfectly! The chicken dishes are seasoned very well and have a fantastic taste. The rice + shrimp/chicken/etc... are HUGE portions as are most of the dishes! You should plan on being hungry when you come here or just plan on taking food home with you!
Prices are overall reasonable - a great meal for 2 can be had for < $20 which works for me (and take some left-overs home!)
The service was always prompt and friendly when we visited and looked after out needs with great attention and detail.
Overall, a fantastic place to enjoy a meal with loved ones while taking-in the wonderful view of the central valley. It's a little ways outside of Atenas, but worth the drive/taxi.