I disagree with some posters here. The islands is packed with waitresses and Internet Acces Point girls that are bored to death by there job. With most of them you can have a good chat, and as Phi Phi Don is still Thailand, everything can happen after very fast. The downside is that you have to compete against a sex starved pack of Thai men.
For the desperate cases, you have freelancers (female and katoye) in the streets close to the bars where they have the kickboxing shows.