I 'm from Gran Canaria.
September use to be wave month, and not so much wind. (50-60% kiting days), but then october and to december, use to have good winds. usually from 15 to 35 knots. Not so strong as June-August where use to have 30-40 knots everyday.
The most used kites here are 7-9, or 6-9 if you go with SB.
You can contact any of the kite/windsurf shops in Gran Canaria,
-www.pozowinds.com (my favourite, ask for Jonas)
Both of them are in Pozo Izquierdo, and they rent, sell, fix anything, or any information about weahter conditions.
Anything else, just ask.