Hi Juan,
Yes Sardinia is big and there are plenty of great places to stay and beaches, some secluded, some rocky, some with fantastic sand - you are truly spoilt for choice.
My favourite area in the island is the vast, unspoilt, wild territory of Baunei, a village in the Ogliastra province home to the amazing Cala Goloritzè beach - a beautiful, secluded beach that you can reach by boat or trekking along a few well-signposted wild trails through the Altopiano del Golgo plateau, which feature incredible rock formations, canyons and several ‘‘nuraghe’’ (ancient megalithic edifices typical of Sardinia). Several other fantastic beaches are found along the incredibly beautiful rocky coast, including the breathtaking sandy beaches of Cala Luna (further north) and Cala Sisine and the nearby fascinating cave called Grotta del Bue Marino right on the crystal blue sea. I would also recommend visiting the amazing canyon called Gole di Gorropu on an excursion trip which you can book via this website. If you check on Google Maps you’ll find all the beaches and the other attractions (when MapMaker was still working I did some tidy-up/additions of markers in the area… :-). While useful to drive around places, your car won’t be of much help to reach the secluded beaches so you better join a boat/trekking tour. The guys at the local tourist agency Cooperativa Goloritzè (+393687028980, goloritze@tiscali.it) have several excursions options.
Baunei is a 3hrs drive from Olbia airport or 2 1/2 hrs from Cagliari Elmas airport. Places to stay in the village or in the nearby Santa Maria Navarrese (a pretty village on the sea) are found on the Baunei local council tourist board’s website here and here.
If you prefer the North West part of the island I would recommend you stay in or around the historic town of Alghero (a Catalan-speaking enclave). My favourite are the beaches (like Baia delle Ninfee) in the area of Capo Caccia and Porto Conte gulf, which features a marine protected area, several caves (like Grotta di Nettuno), cliffs and breathtaking views. Further north, there’s a sandy beach called Spiaggia di Porto Ferro not as busy as those in the Porto Conte area. The coast further north becomes rockier with little access to beaches as far as the abandoned mine village of Argentera, where it becomes secluded and windswept. If you want to reach the NW-most part of the island there are some fine sandy beaches around the town of Stintino, but the absolute star is the Asinara island - a wild, uninhabited, secluded island which is a national park, with several small beaches like the amazing, wild Cala d’Arena. To visit it, check out the official website to book excursions and more info.
Two more great beaches I would like to recommend are on the eastern side of the island, one is called Mari Ermi and the other is Maimoni - both feature fantastic white sand mixed with pink quartz and crystal blue water, and the surronding area is part of the Peninsula of Sinis protected area, visited by several bird species including pink flamingoes. The area is mostly flat and marshy unlike the rocky, mountainous western part of the Ogliastra province. The small historic town of Oristano makes for a great place to stay.
Food-wise Sardinia is home to amazing dishes, cakes, wines and cheeses. You should definitely try the typical ravioli called culurgiones, the flat and crunchy carasau bread by itself or combined with other ingredients, the malloreddus pasta, the sweet seadas (or sebadas) pastries, and the roasted suckling pig called porceddu. If you love cheese, pecorino (firm cheese made form sheep milk) is not to be missed (you’ll see thousands of sheep grazing!) - and if you’re brave enough there’s also a delicacy called ‘‘casu marzu’’ a sheep milk cheese that contains live insect larvae…
Hope you’ll have a great time!
Cheers
F