I can recommend: Recommend Casa Milan Magana Restaurant. Puerto de Mazarron AV.del Castellar
We think you will enjoy this small family restaurant, about 20 minutes drive. Although it is small the chef is very good, preparing some excellent fish dishes, as well as meat etc. There is a meau in English.
Give it a try, we also had an excellent Sunday lunch, the set menu was Sea Bass, beautifully prepared. I would also recommend their fish dish, cooked in an almond sauce.
Enjoy