I recently watched a programme about Portugal which included information on the language, and I'd be very grateful if you could clear up a few points for me, please:
1. After booking a family into his hotel, the clerk said something like “Boa Estadia”, meaning “Have a good stay”, but what is the precise correct form?
2. There's a beach near Lisbon called something like “A costa de Caparina” or something like that, isn't there?
3. The greatest poet of the twentieth century - Fernand Pessoa?
4. A kind of celebration in Lisbon with costumes - As massas de Lisboa?
PS If this is too many questions for one time, please accept my apologies, feel free just to answer one or two and I can send the rest separately.
"Boa estadia", or "Tenham uma boa estadia" are both fine. They're rather formal, though, so if you want to sound a bit more casual you can say "Gozem a vossa estadia" ("Enjoy your stay").
Now, the beach you mentioned isn't called "Costa da Caparina", but "Costa da Caparica". We got it from a Brazilian beach in Rio de Janeiro I think...
And yes, Fernando Pessoa was, without doubt, our greatest poet in the twentieth century. I recommend "Mensagem" and "Ortónimo" for a bit of enjoyable reading. "Mensagem" contains 44 poems about Portugal in the Age of Discovery, and also circles around the mysterious death of our king, D. Sebastian, and how the Nation fell into ruin after it.
As for your last question, I don't think I ever heard about that, but I'll look it up and get back to you as soon as I have information.
Hope I was of help!