Matteo,
Glad you had fun in CR even though you did not kite. I've been to Costa Rica many times, usually between December and April (the dry season).
If you want to kitesurf you should go to Bahia Salinas. It NUKES there from december until May.
Lake Arenal is sketchy for kiting IMHO...I have thought about launching there a few times but it was blowing so hard the windsurfers were getting blown out of the water on 3m sails! No room for error on Arenal.
I have also heard that the seabreeze can produce some nice light wind surf kiting during the summer on the Nicoya Peninsula...anybody out there who can confirm this??
If you want you can read my report from a trip a few years ago at:
http://www.broneah.com/hub/viewtopic...ght=costa+rica
Now that I am more experienced and can handle gusty conditions better I only feel more positive about the place.
The surfing (traditional style) can be awesome year-round...usually an epic spot every 20 km or so
cheers
Roberto