Having the advantage of being Italian, I've been there for the last 5 years in late summer. We usually went to the west coast which is less touristy and very beautiful in terms of natural beaches (I recommend the area around the Sinis peninsula, between Cabras and Oristano) and I've also been to the east (the town of Orosei and the beaches around that coast are also wonderful) and south (equally worth visiting but I remember less about it).
I suggest you get yourself a car as it's necessary to reach the best beaches and towns and public transport doesn't really cover half of the region. In terms of prices, it's certainly cheaper than Corsica while having the same kind of natural beauty and being somewhat less modernized.
Don't expect a good English proficiency among the locals nor a very commercial/touristy treatment (unless you go to a holiday resort or to posh areas) but they're used to having tourists around obviously.