Worst Gaffes
No matter what, never:
Say that Portugal really ought to be part of Spain and quote political, historical and geographical reasons.
Say that you dislike codfish, kale cabbage soup, sardines, fado singing, football and television soap operas.
Say that French wines (or any other wines) are better than Portuguese wines (with the possible exception of rosé wine which is not considered really a wine).
Say the local beer is inferior to any other country’s beer. The same goes for coffee or any other beverage. Or food, for that matter.
Say "Viva o Porto!" (Long live the city of Oporto!) – unless specifically in Oporto.