Panama, Costa Rica, Nicaragua

Since you stated your areas of interest clearly I can tell you what you can find in CR: Isla de Coco is one of the best diving spots in the world (a week "all inclusive" boat ride is $4000-$5000). The caribean side is wonderful for surfing and so are on the pacific, Jaco and the north. More than half the country is reserves so nature is everywhere. People are very hospitable and nice. Zip lines are all over. About Panama I know the archipelag of Bocas Del Toro and I'm going there in 3 weeks time for the second time. Nicaragua? Poor country. All in all CR is the wealthiest in Central America so you can be comfortable, but it has it's price. I live in CR so if you need more info I'll be happy to help.

I've been to Costa Rica and Nicaragua multiple times. I went to Bocas del Toro, Panama once for a few days (flight from Costa Rica) but I don't have as much experience in Panama as Costa Rica and Nicaragua.

Nicaragua, like Guanacaste Costa Rica, is relatively dry compared to the wet climate you find in most of Costa Rica. I am not a surfer but I am told that San Juan del Sur, Nicaragua is a 'world class' surfing destination. Both have nice natural attractions such as volcano -- I'd particularly recommend Monteverde and Manual Antonio park in Costa Rica and Mombacho volcano and the isletas of Lake Nicaragua in Nicaragua. Costa Rica has wider biodiversity in a smaller area but you can find great wildlife in all three countries.

Nicaragua has nice towns (Granada and Leon) with old colonial architecture. Neither Costa Rica or Nicaragua's capital are very attractive for visitors. For a modern city, I hear Panama City is nice but I haven't been there personally.

Nicaragua is cheaper and safer than Panama and Costa Rica. While it's a poor country, the crime is reportedly much lower than it's neighbors. Costa Rica is more developed but yet somehow the roads seem to me to be quite a bit better in Nicaragua. The people of both Costa Rica and Nicaragua are very friendly to American and European visitors, although my wife who is Nicaraguan does not feel the Ticos (Costa Ricans) are friendly -- which may be the case in for her as the two countries have not been very close.