Some Restaurants:

La Pizzeria de Guia - in Guia de Isora - Italian 

El Rincon de la Barriga - in Alcala - Tapas, Fish

Sauco - in Alcala - Fish and Italien inspired - nice location at the sea front

Bar Arepera kilometro 101 - in Santiago del Teide - South American, not very cozy but great Arepas

Chintuma - in Playa San Juan - Mexican cuisine - everything fresh.

Sesto Senso - in Playa San Juan opposite of the beach - Italien inspired. A bit more expensive but great quality.  

Ohana Sunset Club - in Puerto Santiago - All kind of foods and a great few