I’m finishing CDN from Irun tomorrow. WIFI has been highly variable, and just totally dependent on the facility I’m staying in. Generally okay for email, videos, photo editing. Obviously I didn’t stay in every accommodation available along the way, but my experience was that it was better in the newer albergues and the hotels than it was in pensions.
And as you would expect, it was better in cities than out in the country. Depends maybe on the priorities of the owner. Thinking back on it, seems that the better the food was, the worse the WIFI was!
In many places it seemed to get slower and inconsistent as more guests arrived.
My iPad flagged over half of them as having “weak security”, if that is a concern for you.
Related: cell service has been good. I have a good roaming plan with lots of data, so sometimes I just used my iPhone as personal hotspot for the iPad.