Sardinia is besides Santorini my favorite island in the medsea. It has crystal clear water and many sandy coves away from mass tourism. The water is that clear like in the Caribbean. I´ve been only once to Sardinia, but I will definitely come back some day. We flew to Olbia and took a rental car to Porto Cervo. It´s the “place to be” in North Sardinia, the jewel of the Costa Smeralda. In Porto Cervo everything is very luxurious, big yachts and sailing boats, a lot of Golf clubs, celebrities and a great nightlife. You should go there in July/August because in September it´s already too cold and in the evening you have to wear a jacket because of the wind. Also the town is pretty empty already, so it´s better to go in the real High-Season. Without a rental car, there is no possibility to get around, so you should get one.
We stayed in the 5 star Colonna Resort in Porto Cervo. The view is incredible there, from the main terrace you have a wonderful view towards the coast. The hotel is very wide with 60,000 square metres of green parkland. The pools look like terraces and are also quite wide. The fish they serve in the evening menue, is so delicious! I´m not a big fan of buffets (except in All-Incl vacation), so I enjoyed the menu courses a lot! In the morning it´s nice to go jogging, you can talk a run to Faro Capo Ferro , a cute little lighthouse at the coast.
If you want to make some trips, I recommend you to take a ferry (you can take your car with you) to La Maddalena. The coves are even more prettier and there is nearly nobody at the beach. Little piece of heaven! I only stayed there a week in the North. I think it´s better so stay In Sardinia two weeks, one in the North and one week in the South. The island is too big to make day trips to the South Coast, when you live for example in Porto Cervo.