Whether you go to an inexpensive cafe, you'll get a huge portion. If it's fish, there will be at least 3-4 pieces on the plate, plus a side dish.
Traditional dishes of Portuguese cuisine (also called "peasant") include aromatic mashed potato soup with cabbage, beef tripe, braised cod with peas, feijoada (a dish of meat, rice, and red beans), baked trout, and olive caviar.
Prices in most cafes and restaurants in Porto are reasonable. A two-course dinner with wine and coffee will cost around 25-30 EUR.
If you feel hungry while sightseeing
sightseeing, you can grab a big hot francesinha sandwich, Porto's second traditional dish after fish, at any café in Porto. Francesinha is bread, several types of meat and sausages and lots of melted cheese. No wonder that the reviews about this dish are only positive. And of the desserts, be sure to try pastéis, a traditional Portuguese puff pastry basket with custard.
And, of course, any meal in Porto should end with a cup of coffee - uma bica (small), um cafe (large), meia de leite (with milk) or um galao (latte).