Hi Juddy, spent 2weeks at Porto Pollo, one big camground, nothern tip of Sardina was several years ago though, remember lots of rocks and plenty of windsurfers. Got there by car ferry from Genua and back to the mainland near Rom found another spot on the east coast with waves, but less wind. You will need a car to get around.
My sugestion, and I think I may have mentioned it to you already, is take the ferry over to Corsica takes about 40 minutes and check out the beaches around Bonifacio. theres a fantastic spot to the east of Bonifacio, a small island with waist deap flat water. also a few bays to the west, no breaks just wind waves and flatwater.
Corsica is also less touristy, the locals kept on blowing up the hotels of out side investors through out the years.

Spent some time in Sardinia in 2010 and had some great kite sessions there. My favourite was the bay just west of Porto Pollo (See the map and photo). The kiters and poleys stay pretty much apart, except for the odd few. It's a busy place in Summer, but the beach is so long it didn't feel crowded when I was there.
Also had some waves at beach on the west coast just west of Oristano. The wind was great, but the surf was small and not worth writing home about.

Enjoy

Burls