In San Sebastian i have stayed in Hotel Parma perfectly located very close to the old town.
The hotel has parking in the public underground carpark Okendo nearby or use on street parking. We opted for the underground more secure parking.
I have stayed there a couple of times because of proximity to the old town. Although be wary of the one way system to get to the car park it can be painful.
In Burgos i have stayed at the Abba Hotel really nice place and a pleasant walk into town.