I'm a huge fan of all-inclusive resorts, so that is what I tend to lean to.
With that said, Costa Rica is beautiful. I've only been once and want to go back with my family. It is also a favorite of several clients (some have gone back more than once). In the Guanacaste region there are all-inclusives (Secrets and Westin have great reviews, and the "W" recently just starting offering an AI plan). There are also several vendors who put together packages that do not include the AI resorts, that include things on the other side of the island like in La Fortuna. We stayed one night at a hotel in La Fortuna that had pools fed with hot springs, it was really neat. I thought the food was really good. I just had a group return from CR 2 weeks ago that stayed at Secrets and had a blast. They did several excursions, so while they were at AI, they did go do some other activities.