Dagupan exists for bangus and you should plan at least one meal around it. The local preparations are extensive: sinigang na bangus (in tamarind broth), daing na bangus (split and dried), rellenong bangus (deboned, stuffed, and fried), paksiw na bangus (in vinegar and ginger), inihaw na bangus (grilled whole). Anywhere reasonable in town will do them all well.
Beyond bangus, look for pigar-pigar (a Dagupan beef stir-fry with crispy edges), the local puto Calasiao rice cakes, and kakanin sticky-rice sweets at the Magsaysay market. The seafood at the riverside restaurants is the freshest you will find in the country.