The dishes that are actually from here
Cao lầu is the one to start with: noodles, a little broth, pork, herbs. It is a Hoi An bowl, not a generic Vietnamese soup. White rose dumplings are the other local order. Bánh mì here is excellent and ordinary at the same time, which is what you want from a daily sandwich.
What you will pay
Inside the Ancient Town you are on a visitor menu. The food can still be good. You are paying for the chair. A local meal outside that core, the kind of cơm or noodle stall residents use, often lands around 30,000–60,000 dong. Coffee is more. A western brunch is a different budget and a different morning.
Markets in the morning are the honest version of the town: you see what is in season, you eat early, you are done before the groups arrive.