We did Bilbao & San Sebastien a while back.
Only spent a couple of days in Bilbao, was more of an entry point for the rest of the trip. Found some decent restaurants, but don't recall names. The walk along the river by the museum is quite pleasant. We didn't go into the museum, but it's an attractive building to look around.
Coastal road to SS is quite bendy, to the extent that my other half got slightly car sick, which is unlike her, just thought I'd mention it.
We stayed in the Hotel Maria Cristina, and were very happy, although I have no great lasting memories of it. We loved Arzak, but were very disappointed with Mugaritz. Definitely do at least one pintxo tour. We were very fortunate to have Elena Arzak give us her personal recommendations, but hotel reception can probably suggest a good 'route'.
Went to Hondarribia to collect someone from the airport, but don't recall much about the place.
Went to Biarritz for the day. Weather not great but it's a lovely beach to walk along/around. Also take the fernicular for a great view.
Went to Pamplona for the day which was interesting if only for the difference in climate going inland.
Would recommend restaurant Kaia Kaipe in Getaria, some great fish including fresh anchovies straight off the boat.
Roads are typical Spanish (IMO) good quality and not busy. Watch out for the speed cameras especially at tunnels.