The Eurovelo is a network of "15 long distance cycle routes connecting and uniting the whole European continent. The routes can be used by cycle tourists as well as by local people making daily journeys. EuroVelo currently comprises of 15 routes and it is envisaged that the network will be substantially complete by 2020."
Portugal has a route that's part of the Eurovelo, going from south to North of the country by the coastline. "Portugal has wonderful natural conditions for cycling tourism. Although a small country, it has a large variety of landscapes and it is full of cultural richness. There are hundreds of cycle routes throughout the country, either for cycle tourism or mountain biking." - you can download the Eurovelo 1 routes in their website, here, to plan your cycling holidays in Portugal.
The Eurovelo1 is divided in 18 sections and all maps and .GPX files can be consulted and downloaded for free, in their website.