A short country in this directory, and not a thin one. One entry, kept because it is better than most countries manage with six.
February is the answer here as it is in France, though for the opposite reason: not because the country empties, but because the light is kind and the garden is still legible before the summer gets at it.
Monday is the closing day in Lisbon rather more often than the internet admits. Check the hours the week before, then check them again the morning of; I have been wrong about this in three countries.
Porto and Sintra are certainly owed a plate each, and this directory does not yet have one. I would rather leave the country looking short than fill it out with places I have only read about.