Just arrived today to Belmonte, hometown of Pedro Alvares Cabral.
Cycling in Portugal has been so far pretty smooth and finding the right roads reasonably easy.
I normally try not to abuse of gps navigation but a good device supported by valid maps definitely help a lot.
As far as IP roads are concerned, I confirm: IP roads are not allowed to bicycles but if you’re cycling along a national road like N18 that at a certain point for some reason changes classification into an IP road … simply don’t worry. Despite formal regulations, indeed, it seems that if there are not alternatives … well even IP’s are allowed!!
Cycling Portugal is definitely fantastic !!