Do you mean Banana Beach Bar?
If so I went there last week with casual clothes on and it seemed fine with the guys there :] We went at about 11 or so and left there at about 2am or something (that was only because we were flying back that day
) and the crowd was a good amount, not crowded but not empty. The best days are friday and saturday nights - thats when the nightlife in grand baie is at its best I would think. I personally would try and avoid weekdays because its usually not that busy.
Hope you enjoy yourself when you go in october, and be sure to try their cocoloco cocktail lol