We have walked the northern part of the Ruta do Mar (Ribadeo to San Andrés de Teixido) but joined the Inglés at Ferrol. In general terms there were no albergues, we researched for private accommodation and also used the Lugo Amigos links to find a rough guide to the route. We used a paper map, others have used GPS to find their way. Signage varied from good to very poor. Mostly red posts/pointers rather than yellow arrows.
If the route from A Coruña is anything like the earlier sections then you will probably find similar situation.
I suggest looking through the
Ruta do Mar section of the forum to see experiences on that section and also trying to look online for/or contact the local Amigos group (A Coruña rather than Lugo).
(The heading is Ruta do Mar but it is also often listed as Camino del/do Mar - however this can lead to confusion with the route heading north from Portugal.)
Enjoy researching and Buen Camino