Hi Benno!
Try the museum link (in english):
http://www.emfa.pt/www/po/musar/index.php?lang=ing" onclick="window.open(this.href);return false;
There are sections of the Air Museum in some Air Force Bases such as Sintra, Beja, and Ota. Stationed in Sintra are around twenty aircraft, 9 of them in flying condition: Tiger Moth, T-6, Do-27, Auster e Piper Cub. The 1935 Avro 631 Cadet aircraft presently exhibited in the Air Force Headquarters in Lisbon, is a rare specimen that should not be fogotten.
Sintra section may be visited on weekands and feast-days from 10 a.m. to 5 p.m.
About Ota.... well, Ota has a hangar with some interesting aircraft that belong to the Museum but i believe it's not open to the general public. On the other hand, there's a (relatively) new section of the Museum at Ovar, a reserve base in the north of the country.
Any more info feel free to PM me.
Have a nice trip here!!
Abraços