Jeans are fine for La Nouba. You will see an array of clothing styles, from shorts and tee shirts to fancy cocktail dresses. There are people coming straight from the parks and others have date night. There is not a dress code for the show. If you were going to one of the shows in Vegas, or a touring show, I would say dress up a little bit, but Disney has such and array of people attending La Nouba and a lot of people that buy tickets once they are already in town so they did not pack for a special night out... Anything you decide to wear will be fine.