Hi, Kodo,
Welcome to the forum! I'm happy to see a question on the Caminho Portugues from Lisbon, because most people walk only from Porto. The segment south of Porto is changing very rapidly -- when I walked it three years ago, there were no albergues and the marking was bad in some spots. But thanks to the Lisbon' Friends of the Camino group,
http://www.vialusitana.org,that situation is changing. There are now two private albergues on this part, and a lot more awareness of the potential the Caminho has for central Portugal. And the group has a regular "arrow painting" schedule, so the waymarking is really great, I've been told.
You should search the posts listed under the Camino Portugues, here are a couple that talk about the part south of Porto.
el-camino-portugues/topic11285.html
el-camino-portugues/topic11133.html
el-camino-portugues/topic10706.html
el-camino-portugues/topic9418.html
el-camino-portugues/topic9319.html
Well, you get the idea, there are more if you just search through the titles listed. And I'm pretty sure one of those posts lists a link to the on-line guide published by the British Confraternity of St. James, but just in case:
http://www.csj.org.uk/guides-online.htm There is one short guide dedicated exclusively to the Lisbon-Porto segment. I wrote it, and it is getting out of date, but I'm expecting to receive updates from several people who are walking it this summer.
When I walked I saw not one other peregrino, but there seems to be more interest so maybe you will meet some others. Or, maybe you like solitary caminos, in which case this is a great choice. The only drawback I see to Lisbon-Porto are that it is almost entirely on asphalt (even though you are not often on busy roads), but it goes through some very nice places -- Tomar, Coimbra, Conimbriga, Rabacal, etc. Let us know if you go, or if you have any questions after you've had a chance to digest all the information that's already here. Bom caminho, Laurie