Camino Portugues Sintra-Obidos-Porto

Hi, mercian,
If anyone can help you with this, it will be the people at the Via Lusitana, http://www.vialusitana.org They are a "friends of the Camino" group based in Lisbon and have done more than anyone else to promote and waymark the Caminho from Lisbon to Porto. This is not the coastal/western route you describe, though. From Lisbon, the arrows (starting at the cathedral) take you out to the Vasco de Gama bridge, then north along the Tejo a while and eventually to Tomar, Coimbra, Porto.

Their website has a lot of information as well as an email address. Their members speak a variety of languages, so you can write in Spanish, English, Portuguese, German, French, etc., and I'll bet they can answer your questions.

I know that there has been work done on waymarking a coastal route north of Porto, but I am not aware of the route you describe. Bom caminho, Laurie