I am planning a trip myself late April, early March. While researching I have found
www.CostaRicaTicas.com (Mongoring website, locals and fellow mongors). Sign up and ask any questions you may have. Membership does cost about $40/month or 140/lifetime.
check out skokka, and ymas (like backpage), to get a feel of how much and what is out there adveritsing. But it seems since it is legal in Costa Rica, the internet doesn't mean as much as it does here. It is still Meet in person, and go from there.
I am still checking hotels and flights.
Let me know how your plans/trip goes.
Have fun