Fairly easy to find and off the main square, any of your hotels will know where Greens is at. Follow stairs to the left once entering and go upstairs. Greens decor was clean, modern, and inviting. Their staff was very friendly - bothe servers were helpful and one was more knowledgeable about Vegan choices than the other, which helps as their is no word for Vegan in Spanish.
Everything is ala carte, main dishes, sides, etc
I had the Asian vegetables with brown rice and the portion was large and served warm. The only problem was that the server warned me they put salt on it - but I was not prepared for how salty it was, beyond comfortable levels of the others with me as well who had a sample bite.
I also ordered a side of their roasted potatoes, which I asked for no butter, they cooked in oil, and they were a good option.
Finding a lot of Vegan options in Cusco is not very easy, but Greens was a decent option when out for the night.