At first, I was scared to death about the stories I'd heard about the leeches in this park. It seemed as if it was practically guaranteed to be bitten by leeches here! And that was something I wanted to avoid at all cost, disgusted by leeches as I am. So, even though I was scared, we took the necessary precautions (a bit over the top maybe: hiking boots, two pairs of socks, one folded over the openings of the boots so they couldn't slip in, jeans into the other pair of socks, and deet covering it all). We got through without a bite! Even if I walked through the park paranoid as can be. But hey, it doesn't hurt to be careful, I guess. I did look at most folks with flip flops and shorts in horror, though. Oh well.
Anyway, so you *can* get through this forest unscathed. We didn't go far into the forest as it was already a bit later on the day, but the hike was awesome. We didn't see any of the really big fauna but we saw macaques and langurs, which was pretty nice! It was a very enjoyable hike and walking through a rain forest, which I had only seen on national geographic and the like before, was impressive on its own. The songs of the different species of cicada was pretty awe-inspiring and even a bit haunting.
So if you're scared of leeches like I am, don't let yourself be deterred by it. Maybe in the wetter seasons (we were here the beginning of november, start of the dry season), there may be more leeches. But if you take good precautions, you can get through! A final tip would be to take a LOT of water and actually drink it. I'm not a sweater and I was drenched when we finally got back to the entrance.