We are driving the northern route from San Sebastian to Santiago de Compostela and then returning to San Sebastian by way of the wine country. D you think we need to purchase GPS for our rental car? The price seems to be 50% more than the car rental price. Are the main roads well marked? Are there options to GPS I'm not aware of? Thanks for your advice.
Trying to use a strange GPS in a foreign country is a recipe for disaster (well, maybe not that bad but definitely stressful). If you can bring your own GPS unit with you loaded with the maps of Spain. I brought by Garmin with me when we went to Italy for a month and it was extremely helpful.
Are you ( as am I) part of the ever more exclusive segment of the population that doesn't have a smartphone? If you have one, you can get a gps app. (Is that the correct lingo?) If not, you can buy your own GPS very reasonably, so I can't see any point to paying for rental. All that being said, some years ago, we drove from the Basque Country to Oviedo and back on a more inland route, with no in-car technology and very little trouble. We used directions from viamichelin.com. The roads are fine and well sign-posted. The only caveat about viamichelin is that its time estimates are overly optimistic. Add up to 25%.
I never use GPS but also have experienced that the roads under discussion are pretty straight and well signed. Following directions to a town center also well signed. If it's a town covered in Rick's guidebook, he'll mention some navigation and parking tips. Rural wineries or restaurants can be harder to find, off the main highways, but could be researched in advance with GoogleMaps and ViaMichelin. If you have a mobile computing device with you, you might look for instructions for downloading Google Maps for offline use.
I wouldn't spend the extra money. I have my U.S. one loaded with European maps, but all the main roads are well marked. The northern route is pretty straight forward. I only use GPS to get out of some towns to ensure I'm leaving it in the right direction. If you're concerned at all, once you know your route, go to Google maps and do a virtual drive of parts of it. You can take some screen shots, then print them out. If you drive on some smaller roads the road number may change between areas so it's helpful to know some of the towns you'll be passing along your route and use them as a guide.