I also went to Costa Rica for my honeymoon...wonderful place.
Do be aware of the humidity...especially when you go from a cool, air conditioned room, out into the hot humid air. Condensation will form on everything...so try to let your camera gear warm up before you take it out of your bag. It might also be a good idea to have some desiccant (silica gel) in your bag, to absorb moisture.
I took my Computrekker AW (all weather) bag, which has a built-in rain cover...and it came in very handy. We did go there during the rainy season...so we got a lot of rain.
I did soak my camera once...
We went on a 'zip line' tour of the rain forest canopy...it was great. We had to ride horses up to the 'base camp' and because we had to wear harness for the zip line, I had to leave my camera bag. It wasn't raining, so I took the camera along. By the time we had hiked up to the starting point, it was raining, and soon it was a torrential downpour. To top it off, I had to take my hands off of the camera to hold onto the rigging, when zipping from tree to tree. I did have a shower cap and a small plastic bag to cover my camera...but it got soaked, non the less. I probably should have taken the battery out, but I just kept it as dry as possible...and got some great shots on the ride back from base camp. The rear LCD screen fogged up (on the inside) and it took almost 24 hours before it dried out completely...but that was the only problem. The camera is still working well, a few years later.
As mentioned, the light really isn't very good, once you get under the canopy of the trees. If you don't have a hot-shoe flash...I would recommend getting one. Also, if you really want to get good wildlife shots...I would recommend the
'Better Beamer'.
HERE are my photos from the trip.