If Algarve, you would need to go to Lagos or Albuferia, the later has a strip though & might be too clubby for girls of 15, Lagos has an old town with loads of bars, cafes and restaurants for an evening.
You are more likely to get a 'good pool scene' in an AI hotel - music playing and pool games. In Algarve there is the Paraiso de Albuferia and a First Choice Holiday Village.
Lykia World (bit isolated) and the Belcekic Beach Club in Olu Deniz, Turkey are both lively during the day but a bit expensive.
Another place you could look for an AI is the cheaper Greek Islands, Kos or Corfu if you pick the right resort should be lively enough - not Kavos in Corfu as it's club18-30.
Mainland Spain, one of the Costa's ? There are forums about all of them. Costa del Sol, Nerja was a bit lively at night time, but you would need to pick the right hotel for daytime activities?
The Costa Dorada/Salou is good if the 15 year olds would like the distraction of a theme park, as it has Port Aventura, they could get a three visit ticket which would give them a lot of daytime entertainment, plus there are two waterparks. Mainly HB hotels but at least your breakfast and dinner would be paid for upfront.
So difficult holidaying with teenagers - been doing it for the last three or four years - nightmare to keep everyone happy
In an hotel, would you want 2 rooms or three rooms. if you need two doubles and a single it will push the price up ? You may need to look for some kind of aparthotel which are hard to find.