Hello rachex 1984,
Portugal is a country with big diversity of landscapes and some areas are still prety unspoilt for example: All the border region with Spain ( Starting in Geres - Northwest ( National Park ) passing by Montesinho ( Northeast ) and after that, all the way down to Algarve ( Most Southern region of continental Portugal ) you have many chances to enjoy tracks and also visiting many castles and small villages ( some of them almost empty ) and learn more about our historical heritage and culture ( near 900 years of history as Portugal ); A good project could be, starting in Geres ( you could stay in youthhostels or residentials it´s good value for money ) then East and after go South ( passing eventualy through Estrela ( Star) Mountain- Serra estrela in portuguese 2ooo meters altitude and fantastic tracks ) but to give you more tips, please try to inform us things, such as: how many days, budget , how many people travelling, levels of difficulty and preparation of the group, in what month are you comming, because here, specially in Alentejo and Algarve ( the 2 most southern regions ) might be a little unconfortable to ride ( high temperatures in July-August ), etc..
When you say more about your project, the Mountain-Bike groups ( there are many in Portugal ) and associations will be glad to help you and even send you recorded tracks for the gps.
Looking forward to ear from you
Regards
Ko
Ta
M