I stayed here in April 2012, travelling alone. The hostel is located very near to the National Park, the "center" of Cahuita and the bus stop. I got a single-room for 15$/night. The room was good, with a big bed covered by a moskito-net (which you need!). The bathroom was part of the room, a bit unusual, but nothing to complain about. I felt absolutely safe here. The rooms are tidy and are cleaned daily.
The owner named Willeke, a Dutch hippie in her 50s, is absolutely helpful, she even picked me up at the bus stop, The hostel in general seems very well managed, the community area is lovely and the garden very colorful. However, Secret Garden is not really a hostel, with lots of the guests being couples. So don't expect to meet a huge party happening- well, there is not much to party in Cahuita anyways. If you want to cook a lot in the community kitchen you might want to choose another hostel, because the kitchen is small and was a bit dirty.
All in all I would recommend Secret Garden to everyone visiting Cahuita!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.