Hi AJ,
I walked the Norte for two weeks last year. I started on the 14th of July. Before I went I was worried, that there would be limited accommodation. With one or two exceptions, there was room in most of the albergues. There were enough beds for pilgrims for the first four or five days, as not as many people walked from Irun to Bilbao. After Bilbao, it got busier, but I think most places were prepared for this increase, with alternative accommodation, camping, sleeping on mats, etc.
Irun - I arrived at the municipal albergue quite late; around nine, but there were still five or six beds left. The hospitaleros were lovely!
San Sebastian. The albergue is in a secondary school. The ground floor is converted into an albergue for the summer months. A large group of teenagers were walking with their teachers and therefore, the albergue was full by four o'clock. I stayed in this albergue but there is a hostel close by as well.
Zarautz. I think I stayed in the town hall, with lots of artwork. There weren't as many beds as San Sebastien. I got there before three and there was already a queue of rucksacks/shoes! It filled up quickly but there was a list of alternative accommodation. I think I photographed this list and I will post it later this evening.
Deba. This albergue was a converted train station. It was a small albergue and again filled up quite quickly, but some pilgrims slept on the floor. The procedure for getting a bed was a little bit different to normal, in that you got your bed number and key (loved this - you could come and go as you wanted!) from the tourist office.
Merkina Xemein. I felt that the walk from Deba to Merkina Xemein was the most difficult. There were two albergues here and there seemed to be plenty of beds (overflow room as well) in the convent.
Gernika. There are no albergues here. I stayed in the youth hostel. There were plenty of beds and the hostel was adequate. There was also accommodation, in a bar in the middle of the countryside, about 7km before Gernika, for about 10 euros.
Lezana I stayed in the town hall. There were about twenty beds, but I don't think many pilgrims stop here.
Bilbao My initial plan was to walk the short distance to Bilbao, see the sights and then stay in the hostel. However, the hostel is very far from the camino and Bilbao city centre. While there was nothing wrong with the hostel; there were hardly anyone there and it felt a bit soulless. I felt as if I had stepped off the camino. I changed my mind and walked the extra few km to Portugalete.
Portugalete I arrived here late - a little after four and I got the last bed. However, they allowed pilgrims who arrived later, to sleep on the floor or pitch tents in the yard.
Castro Urdiales. The hostel was already full by the time I arrived. About five of us slept on the floor. This was fine! However, the showers were horrific. I have stayed in all sort of albergues. I am very grateful for all the infrastructure, volunteers, communities, that make the camino possible, but this is where I draw the line. I would have prebooked accommodation elsewhere.
Santonas. I stayed in the youth hostel, as I did not want to walk any further. The hostel itself was full. Instead there was a sea of four man tents in the back, for the pilgrims who had not prebooked! I was so tired, that I would have slept anywhere. I slept very well. Showers etc. were good.
Guemes. Other people have written about Guemes already. Plenty of beds.
Santa Cruz de Bezana. This was a lovely private hostel. The owners were lovely and it was one of the many highlights of the camino.
Santillana Del Mar. I stayed in the monastery, but there is plenty of accommodation. They leave a page outside the albergue, numbered 1-16 (16 beds). You write your name down and then you can come back later; when the albergue is open.
San Vincente de la Barquera I think there were about forty beds. It was definitely unusual. Almost everyone I had met in the previous fortnight stayed here. I have never been kept awake by a smell before. This was a first! However, it is the people, rather than the place, that makes an albergue.
In short, I loved walking the Norte. It is so beautiful. I am quite a slow walker, but I still got a bed, without any need to prebook. However, there are one or two places, where I would have prebooked (just for more comfort etc.)
Hope this is of help!