If you refer to beach areas the your answer is Varadero. There are no other beach areas in Cuba that offer as much night life as Varadero. Locations like Guardalavaca, Cayo Coco, Cayo Largo, Cayo Santa Maria, etc base their entertainment on the hotel premises. If you are looking for night life then Havana, Varadero, Trinidad and Cienfuegos will be your answer.