We spent almost 3 weeks in Spain last month. We started in Valenicia and spent time with a relative, then took we trains and buses to stay in Granada, Ronda, La Linea/Gibraltar, Tarifa/Morocco, Seville, flew back to Valencia then train up to Barcelona for a few days, then flew home. We logged in a lot of travel and walking miles, saw a lot, and had an enjoyable time.
Although Spain looks small on a map, it is a pretty big country and not all of it is connected by high speed rail. In fact, some of the cities we stayed in did not have direct buses between them, so we had to be creative and were able to cobble together different bus company routes to get from one place to another. We did one transfer in Malaga, and another was actually at a bus stop in San Pedro de la Alcantara. Be better to hop-scotch to different cities rather than try to do travels from a central location.
I made it more stressful working the travel itinerary less two weeks before our trip but it worked out great. Next time I am going to try to do things in a more leisurely fashion.