First suggestion: if you are undecided to stay in Quepos or Manuel Antonio, do not hesitate to choose Manuel Antonio. It is not so crowded as Quepos and the beach is amazing.
These Cabinas are very small (only 3 room) but nice and cozy. The rooms are big and clean, they have air conditioned, tv and private bathroom with hot showers (that in Costa Rica are not taken for granted!). The owner, Marc is a Spanish and he is very kind. They cost 25$ per person per night but they are close to the beach and in a quite area.
I would suggest this place to people who wanted a compromise beetween low cost and confort. If you are backpackers just interested in the price, there is another hostel in Manuel Antonio called Costa Linda, that cost 9 $ per night. However I heard some complaints about it. Have fun in Manuel Antonio! more