The answer, most of the times, is yes.
If you are going to Sardinia for a short city break of two or three days in Cagliari or Alghero, then you probably do not need it.
The airports are not too far from the towns and you can easily get a cab from there. You can visit the city centre by foot and you can reach the local beaches by bus, even if the public transport can be a little bit slow…
If you are planning a tour of different areas of Sardinia also taking many day excursions or visiting the most secluded areas of the island, then you really need to hire a car.
Top tips:
1) Sardinian drivers are very “creative”, as Luca says, so be careful
2) Directions are not always good, so check your route on recent maps before you start going.
Ciao
Manu

January 18th, 2009 at 11:38 pm
I totally agree. If you have more than a few days car will allow you to see all the beautiful beaches that are all around Sardinia. We unintentionally discovered a lot of them while driving from one city to another.
December 27th, 2010 at 2:39 pm
I agree that a car can be useful but having visited beautiful Sardinia 7 times i would recommend using public transport. It is the best way to meet people and you can relax while sightseeing. It is also very inexpensive. On my first trip to Sardinia we flew to Alghero and got a tasxi into town. After a couple of days we got a bus to Cagliari. Next day we took a train to Mandas and from there we got the Trentino Verde to Arbatax. 3 days later we caught a bus to Tortoli and then got a connection to Dorgali which took over through Baunei and over the Otientale Sarda. At Dorgali we caught another bus to Cala Gonone where we spent 5 days. Our return journey took us by bus to Nuoro where we changed for Alghero. A fantastic trip. If you would like to walk in the remote mountains and gorge it would be worth hiring a car for a few days.