For the Spanish regions, I would recommend renting a car, staying for at least a week in the area (Rías Baixas and/or Priorat) and roaming around checking out the wine bars in the towns near the wineries. Some wineries are more receptive to guests than others, but you can nearly always sample the wines in the adjacent towns and buy at bodegas.
If you want to visit the wineries, I would call ahead (email can be dicey). Many only allow visits on certain months, days and times.
Here's the info from the Rías Baixas D.O. (look under routes):
And better sites (in Spanish) with info on routes in Galicia:
And a list of all the wineries with phone numbers:
Here are some similar links for Priorat (in Spanish):
http://elmundovino.elmundo.es/elmundo... (list of bodegas, click for phone numbers)
I am hoping to do some wine touring in Spain in the near future. I haven't looked a lot yet but this company has several wine theme tours, self drive or driven, quickly perusing the site I see Galicia and Basque country, although I have seen Rioja on the site too.