Without any doubt Sa Caleta is our favourite by far. It's located in the small cala. The beach is surrounded by dramatic red cliffs, creating a feeling of seclusion. Its sandy beach is quite shallow and clean water invites for a dive. The food is made for locals, not tourists. It is open all year round and its only 15 minutes by car.
Restaurante Ca n'Alfredo is the oldest and probably most prominent in Ibiza. It is located in the old part of Ibiza at Paseo de Vara de Rey which is a no car pedestrian zone and just 15 minutes from Villa Aloe Ibiza. It offers many seasonal dishes like the typical Salsa de Nadal which is traditionally served around Christmas. Our advice: it's delicious but do not look into the recipe before trying it!
Keep in mind that in April and May each year there is a an Ibiza Sabor (Ibiza Taste) period when you can taste best dishes from top of Ibiza's restaurants at a fraction of the cost (usually €25-30 per person).