Hi,
I think I can give you some tips.
Of course, you can camp at POE, there is a free one and another one (not free...).
To be honest, prefer the one that pays off. The other one is regularly victim of robbery.
Between Noumea and Poé, you can go to OUANO, on the left of the surf camp. Good spot when windy.
In NOUMEA, 2 spots, very easy access : Le Meridien and Cote Blanche.
Ilot Maitre is a very good one as well, it's juste around 15mn from noumea by boat (2000 CFP return). Different ways to go overthere : Taxi Boat (the yellow boat in L'Anse Vanta), or by the Coral Palms (the Escapade's boat).
September is a little bit early in the wind season. The best moment is December.