Two things to understand: the fish comes ashore at a working caleta east of town, and the rest of the eating is stacked up the two tourist hills at tourist prices.
Caleta Portales — the working fish landing
The boats come in at the caleta on Avenida España, east of the centre, with sea lions and pelicans waiting at the quay for scraps. Chile's national tourism board points visitors here for fresh seafood; the comedores above the landing serve it fried at lunchtime and shut in the afternoon.
Almirante Montt and Paseo Dimalow — the eating streets
The restaurant strip climbs Cerro Alegre from Plaza Aníbal Pinto: this is where the menus are in English, the wine lists are long and the bill is two to three times what the same plate costs down in El Plan. Best used for one dinner with a view rather than every meal.
Fauna, Pasaje Dimalow 166
The restaurant of the Fauna hotel up on Cerro Alegre, open to non-guests every day from 12:30 to 22:00, phone +56 32 2121408 for a table. It is the reliable sit-down option on that side of the hill; book ahead at weekends.
Chorrillana, and how it is actually ordered
The Valparaíso plate — chips under beef, fried onion and egg — is built for sharing, and one is genuinely dinner for three people with beer. Ordering one each is a rookie mistake and an expensive one.