The squad assembled at a hotel in Cascais and was training at neighbouring Oeiras last week.
Latvia have chosen Lagos as their home base to prepare for the
match.
Portugal are currently second in their qualifying group, on six points, three behind leaders Switzerland, while Latvia have three points from their first three matches.
The match this Sunday in Faro, kicks off at 7.45pm with only a handful of tickets remaining for the fixture at the time of going to press.