Thanks guys, Gabri, yes I was really hoping for Agkistrodon and there were people who saw 2 that night, but I did not unfortunately, I wish I had some more time there, it was sort of a race to flamingo and back while I was constantly almost falling asleep.
Mathijs, I really had high hopes for amphibians in Monteverde and I met the herpetologist there who is there for more then 20 years, he also told a story like that, Boa constrictors were already found in this place, so in a couple of years you will also find eyelash vipers there.
Robin, I had no locations at all, everything except CRARC was a wild guess, I have no idea where Atelopus could be found.
Jeroen, moon state was close to 'new moon', but can't remember which way it was going. Some rain might help also.. And your eastern family trip looks great and gave me some future ideas