Minho food is hearty and unfussy — caldo verde (kale and potato soup with a ring of chouriço), bacalhau (salt cod) in a dozen preparations, rojões (braised pork with offal and chestnuts), and the local lampreia (lamprey) in season from January to April. Lamprey is an acquired taste but the Lima is one of the last rivers in Portugal where it is caught in any quantity, and local restaurants take it seriously.
The restaurants along the riverside and in the Largo de Camões area offer good value, with most main courses well under €15. Wash everything down with the house vinho verde — you'll pay almost nothing for local carafes and they're almost always good.