My wife and I started in Lisbon and crossed into Spain near Rosal de le Frontera. Our route through Spain took us to Seville, Cordoba, Valentia, Barcelona, and north to the French border. While our route was not very straight it did not give me a feel for the density of small villages clustered around a larger town. There didn't seem to be towns spaced as close as 30 km (19 miles) in the Rosal de le Frontera to Valentia. portion of the route, but that was a "linear" perspective. We were there in late June and early July with temperatures reaching 43 C. Also, most of the towns "closed down" between I:00 pm and 6-7 pm. I don't think southern Spain would meet your criteria, but my wife thinks that Cordoba might have some possibities. One thing you might do is use Google Maps "Street View ", and check out the small villages around your potential home base. Cordoba might be a good place to try this.
Aracena--It seemed like most of the towns we stopped at were on a hill.
From Valencia to Barcelona is a nice ride but there are a lot of hills. You might look at Tarragona using Google Maps Street View to get a sense of the surrounding villages and the terrain. My wife played with Google maps a little and Taragona has some potential. We stayed there one night but did not venture far from the coast.
Good luck, and enjoy your rides.