I would tell everyone with reckless abandon

I’d probably tell a few select people.

I would probably tell someone so they know what happened to me if I ever suddenly disappear. the government did it

I'd tell my closest friends, preferably the ones who read because they tend to have open minds about crazy things.

I'd probably tell everyone and look down at those who assume I'm crazy and argue with them tooth and nail.

Without proof I'd likely keep it to myself.

I'd keep it to myself, but not because people would think I was crazy, but because I would have some empathy for the creature and don't want every nutter human descending upon the area making their life hell