There's L'Entrecote St-Jean inside the walls of the Old City on St-Jean street. Good steak & fries with a great salad, steaks are 5, 7, or 9 oz. Prices are reasonable (24-30$, including desert) and service is personable.
A place to avoid: Aux Vieux-Canons, on Grande-Allée. Food is mediocre at best, service the same, only good thing is the great terrace! Tourist trap!
There's also Gambrinus, on street du Fort, in front of Chateau Frontenac. The food is great, surprising and stylish, French/Italian (not typical pasta), but the prices are a bit high (30-35$). Try to go for lunch on a week-day, for 10-15$ you get a complete meal and can sample the creative dishes. For dinner in the week-end, reservations are preferable.