Fiesta - nista. A person who goes to festivals.
Jack: "Who is that?"
Jill: "That is Billy. He's a fiestanista. He just got back from Bannaroo and is making plans to hit Burning Man."
"Let's get out of this bar. Too many fiestanistas. Next thing you know, everyone is going to break out the jembes"
"I'm going to meet some other fiestanistas down in Austin for SxSW."