It is too late to help Patchnomad, but I don’t think there is an “albergue” that pilgrims know of in San Sebastián or Bilbao. There might be other lower-cost lodging available.
I passed by the city twice. The first time I stayed in a donation-based religious group run housing in the mountain just before descending to the city, and the second time in a hotel in the city. The city’s old section is well known for excellent pintxos so if you happened to stay in San Sebastián, don’t miss the opportunity.