This advice regularly crops up, "eat where the locals eat" is the usual suggestion when the question of restaurant recommendations appear. I have always disagreed with this advice because a) how does one identify who is local or not? And b) tastes are subjective and popularity doesn't always equal quality. A good example of this I experienced yesterday.
My two sons and I had spent much of yesterday morning wandering around Estepona's old town and we stopped for lunch at a very good restaurant that I had eaten at several times previously so knew the food was excellent. Admittedly it was early for Spain, 13:00, but it was Sunday and a lot of people were setling down for lunch. This particular restaurant has limited seating outside, on the table to my right were a French couple whilst the couple on my left were German, the tables inside were empty. The food was, as usual, excellent. The prices on the higher side than others in the surrounding area.
After we left we passed a restaurant that was almost full to capacity, the only language I heard was Spanish, whether they were locals or Spanish tourists who knows, it was impossible to know without asking them. It was clearly a popular place but one look at the food and prices said it all. It was cheap and the food reflected it. Very unappetising, a lot of stuff evidently brought in pre-prepared and heated up but the prices were clearly the attraction.
So if you are looking for good food don't follow the "eat where the locals eat" advice because popularity isn't a sure sign of quality.