That sort of advice never made sense to me. I used to live in a very non-touristic place, and there were tons of terrible food places, despite only being able to live off "the locals" who were supposed to know better.
> there are a lot of places where the locals goes because they are cheap not because they are good
Por que no los dos? The whole cheap/good-choose-one thing is not universal in my experience. I've rarely been steered wrong by trying out the cheap-and-cheerful local option