The AGACS (Galician Association) was repainting yellow arrows last year between Lisbon and Porto (until this moment, the worst marked part of the Portuguese Camino). After that, they published a free guide Lisbon-Santiago. As it's free, it's available in http://www.amigosdelcamino.com
About Albergues, I think the first one is in San Pedro de Rates (between Porto and Barcelos). I've heard there was another one in Barcelos, but I'm not sure. The one in Ponte de Lima will be ready soon. Another one in Rubiaes, just after the "Serra do Labruja". And the last one in Portugal just in Valenca do Minho, two kilometres before arriving to Tui.
In Spain, you have albergues in Tui, Porriño, Redondela, Pontevedra, ... ¡No albergue in Caldas de Rei! try an hostal, Padron, Teo and Santiago.
About stamps, I would recommend you to obtain the "carimbos" in the fire stations. The one in Barcelos is in Barcelinhos, just before pass the river to Barcelos. There's another one in Ponte de Lima. Sometimes, the "bombeiros" has offered the pilgrims some place to pass the night.
There's a very interesting "carimbo" in the church "S. Bom Jesus da Cruz" in Barcelos. Interesting church to visit, Barcelos is not only the archeologic Museum. In that church, the Carimbo is pressed on your credential raised, without ink.
The albergues from the spanish side ... I found it opened in february, so I imagine it are opened now.
The portuguese side ... I don't know. It didn't exist three years ago.
The one in Valenca don Minho has a paper outside the door with the mobile number of the hospitalero. So, may be closed, but it's possible to sleep in. I suppose it's the same in others, in other Caminos it's the normal way to obtain the keys of the albergue.