We always make fun of people equiped as if they would go on a Safari when they arrive at Palma Sur Airport. Really, Costa Rica is a very civilized and absolutley beautiful country. You won't need to fend off wildlife but just relax and enjoy living with it for awhile. We recommend bringing at least one flashlight with extra batteries, sunscreen and sunhat, long sleeve shirt and pants, boots (especially in the rainy season).
I first came to Costa Rica in 1998. I fell in love with the country right away for so many reasons. I have been coming, living and unfortunately never staying off and on since.