Bali is now the number one night life spot in Asia -far from the elitist Shangai and Singapore, the sad Patpong, or the 2 o'clock curfew of Pukhet or Goa.
There are bars and night clubs in Bali for all type of crowd, for all age, from the australian Billy's where toddlers dance in the arms in the grand-mother to the upper-middle-class-middle-age Living room or the surfers hormones boosted MBargo. See the map next and below for more details.

Even for the most resilient of the tourist in Bali, libido will rise quickly. It is easy to meet people and tourists from all over the world and indonesians will mix easely, eager for fun and love. The asian way of looking at sex and gender is different from the western ways, the age difference apply less while statut and wealth definitively matter. A note for the young western male, in Asia, the virility atributes, such as facial hair, shaved hair and though attitude scare the girls, these are symbols of violence they tend to avoid. In case those apparences can't be changed, try a genuine smile... For the western girl, strolling in bikini along the streets won't be understand by indonesian as the normal way for a girl awaiting for the only one, white knight or healthy surfer, for which she offers her best, the natural way. It will be seen as seeking sexe...
There is prostitution in Bali, girls and boys coming mainly from other indonesian islands (not to say java). Nowdays, a balinese girl may marry a foreigner, but the beginnings will be secret (even if pregnancies before weeding are a normal occurence in the balinese society).
The difference beetwen a prostitute and a jakarta business women doesn't usually lie in the clothing and the attitude, there are no obviuos tell tales sign (even if in some of the bar near the double-six street, the Dyanapura street or in Kuta night-club, the ladies dressed in black with calculating eyes look and are the type). The business women will pay for the dinner.