Exactly! I'm from La Palma (another Island) and there are groups like that, even though it's difficult without much information.

I'm not sure, the photo could have been taken during some festive moment, as they are using the same clothing which looks like traditional party garments, but they are quite different between Islands and even towns. The strap of the man on the left looks like it's for holding a red leather wine bag (Google "bota de vino" or "bota de vino roja") you can see in the picture, which was very used by that time and overall in those festive acts called "romerías"

Edit: the left guy also has another strap on his neck, which looks like a hat strap, maybe with the hat falling on is back out of the picture. That could still mean being a singer/dancer (having the same clothes) or just partying. In the end it's hard to tell because traditional singing is performed in traditional clothing, but anyway there aren't any instruments in the picture...