We could not quite decide where to stay for our first night in Sardinia, as Bosa has so many hotels and B&B. We finally opted for the Al Gabbiano Hotel because of its position and facilities. As it turned out, we have made the best possible choice.
The hotel is virtually on the beach, our room at the top floor had a terrific view, was large and very comfortable, and it had a balcony with a gorgeous view, plus a table on which we had a great pizza brought from the restaurant downstairs, accompanied by a bottle of local sparkling wine and grappa, all this whilst the sun was setting down right in front of us. The sea was so calm and beautiful, both at night and in the morning, and the breakfast was more than sufficient, great coffee, cakes, ham/salami/cheese, etc. It all worked out extremely well and very inexpensively. The picturesque Bosa is supposed to be a 2km walk - we did not verify that and preferred to drive, which we would do again, actually. And if you do, try parking before crossing the bridge to Bosa on foot, rather than driving, as there seemed to be no parking spaces in town. On the other hand, take your car to the top of the castle, where you can park for free.