I am from Costa Rica and I will be getting married in Guanacaste May 2012 as well. Have you chosen your venue yet?
I did not hire a planner to be honest, as a Costa Rican, that is kind of a new concept for me. I am sure that wealthy costaricans use them all the time but they cater mostly to Americans. Do not book all of your wedding items through the hotel they will charge you a lot for very simple things. For example the on-site wedding coordinator quote $20 for each boutonniere. When they are at most $4 if you hire a florist or a decoration company to do it. Also the decoration they provide is very basic. I wanted more (drapes, lounge furniture, up lighting) so I just draft a request for proposal and mail it to the decoration companies I choose.
I am still trying to find some vendors, for music (reception and ceremony), and entertainment. Overall I think I am doing very well on my own.
PS. If you have the money hire a WP they can take off you all the stress of the planning.
Some affordable WP I had some comunication with and may hire for DOC only.
www.costaricanweddingparadise.com around $1800
www.crystalweddingplanner.com around $ 800
e-mail me maybe we can exchange some vendor information. firstname.lastname@example.org