Had a great 2-night stay in November at Arenal Green! Wish we could have stayed longer. Very secluded and quiet (we did hear the rooster, but it didn't bother us). The cabin was basic, but very clean and cozy. The woodwork in the cabin was beautiful, and we spent a lot of time just lounging in the hammock on our porch, looking at the volcano during the day, and the stars at night.
Breakfast was tasty, basic typical food, with good coffee and juice. The location of the hotel was ideal for going to Cerro Chato (which is much harder to hike than you think it is!! And we are young and workout/hike regularly) and La Fortuna. We spent an evening at Paradise Hot Springs, which we also recommend, particularly during the low season.
Overall, our experience at Arenal Green was VERY positive, and we will absolutely be going back. Monica, at the front desk, was so friendly and helpful, suggesting several soda's in La Fortuna.
The ONE and only negative thing I could say (and it was only a minor negative point) was that one night we went to the front desk to try to have the hotel book our tickets to the hot springs. There was a younger boy (teenage?) working there, and he was not exactly friendly. He ended up ignoring us while he played on the computer, then ignored us again when our Spanish skills were not so on-par (he spoke no English). It was fine, and we booked the hot springs ourselves for the same price, but still.
That little incident was so minor that it didn't at all take away from our amazing experience at this hotel, and we are very much looking forward to a longer stay there!