Update

Okay, Perspicacious Reader.
I pulled an all-nighter and did some exhaustive research. To wit, I hit the button on the computer that made the link below work, the one to the website for Klezfiesta. Looking at the website makes the event seem like a real thing, with, eg, pictures and text that don't look fake at all. So there probably is a real klezmer festival in Argentina. Getting to the bottom of this type of mystery using research, moxie, and good, old-fashioned shoe leather is just the type of thing we do here at The Vicious Traveller, so you best get used to it, buddy!