I don't know if there is an actual "area" in Benidorm, but there are plenty on the street as it were.
Just take a stroll and you should be able to pick them out. They will probably spot you and make first contact too (if your walking along on your lonesome).
They don't necessarily stand alone but have seen little groups of them.
Right time to get the street map out:
The main streets that I saw them in were Av. del Mediterraneo, as far along as the Av. Ametlla de Mar.
Try Calle Gerona, particularly towards the junction with Calle Derramador.
Calle Lepanto wasn't without a few neither.
It just so happens that there are plenty of drinking establishments here too so if there are no walkers to be found you can just get drunk instead (but not both!)
Probably best to stroll around later in the evening, it may be easier to spot.
There are at least a couple of places to visit in this general area too. (time for google street view, lol)
Try a walk along Av.Dr.Orts Llorca (heading towards the beach on the left hand side of the road) think there is actually two on this street.
But they don't advertise so keep your eyes open, you might be lucky the girls may be standing out side the "shop", lol.
Another can be found along the Calle Gerona towards Calle Derramador, very local to the Ambassador Playa II.
Find the cafe with the "John & Josephs" sign, down the lane to the left hand side of it. There is a place on that lane, the same lane as Black Chicken.
Don't know anywhere else as that was the area local to hotel, in 2011.
There as also a strip joint in this area, or more towards Av.de Europa, forget if you pass that street or not, I'm not remembering its location at present. (some of the group visited it, lol).