I stayed at this hostel by accident - having got bumped from another up the road. However, it turned out to be a 'good' accident, as Arenal Hostel Resort turned out to be if not the best, then one of the best places I stayed during a four month trip to S. America and Central America.
You were immediately made to feel extremely welcome by the staff, provided with a free cocktail served by the poolside bar, and given advice about what to see and do in the area. Staff also booked trips on your behalf.
The rooms were spotlessly clean as was the en suite bathroom. Breakfasts were good value - plenty to eat and a good choice of food. For me the the lovely garden with its pool was the winner .... so relaxing to come back to, hot and sticky after a day out, and able to take a dunk in the pool and then chill with a drink in one of the hammocks. Bliss. In fact it felt more like a 'resort' than a 'backpackers'. The challenge for the Resort is to maintain this high level of service and accommodation...and I hope they continue to rise to it - as they have a winner here - and I'd say, the best place to stay in La Fortuna!