If you go - go to the west coast and the mountains. Stay out of the city. (I spent 90% of my time in the mountains and coast.) Some of the pictures I've posted are from there.

And the people are very friendly. I enjoyed Costa Rica. Did it for my 50th birthday via G Adventures (it's a Canadian sustainable travel group - that helps local businesses, stays at local hotels, and travels sustainably). Also reasonable group tours - with no more than maybe 10-12 people on a tour. You get to do your own thing or stuff with the group.