Two Aussie seniors on a walking holiday

This isn't going to be of much help, but I spent 89 days in Spain last year, seeing quite a bit of the country but skipping Andalucía and the area around Valencia. With that caveat, I do have an opinion about pretty countryside.

• The Picos de Europa area in Cantabria/Asturias is spectacularly beautiful and I think the most dramatic area in Spain (mountains, gorges, green), but I fear you'll be a bit too early for that region. It would be worth Googling to see whether I might perhaps be wrong.

• The second prettiest area I saw was the Basque Country. It's really lovely and you have some very worthwhile cities to retreat to (Bilbao, San Sebastian, Vitoria-Gasteiz), plus there are nice coastal villages, albeit now developed for tourism. The thing is, from the Basque Country through Cantabria and Asturias to Galicia (some exceptions on the Galician coast), a wide band of territory runs much cooler and wetter than the rest of the country. Whether that would be an area good for hiking in May might depend upon your tolerance for hiking in the rain (possibly quite chilly rain). And of course your meteorological luck. Note that this is along the route of one of the pilgrimage paths to Santiago de Compostela, so it is certainly walkable. There's a great deal of information on the internet about the route, and there are some guidebooks available.

• Galicia is also pretty. Much of it is green and hilly; I just thought it was a bit less dramatic than the Basque Country. I think it's worth investigating this area. Although Santiago de Compostela (an interior city) is sort of notorious for lack of sunshine, the coastal cities of Pontevedra and A Coruna are sunnier; they can actually be hot in mid-summer. And Galicia has a lot of nice coastal towns that I assume share those two cities' good weather.

• Catalunya might be ideal from the weather standpoint. The temps there (aside from mountainous areas) are more moderate than you'll find to the south or farther west. I hope Enric notices this thread and gives you some suggestions. I remember thinking that the latter part of the bus ride from Figueres to Cadaques was lovely. The area over near Andorra is very pretty, but you're getting into mountains there. I got near the Spanish Pyrenees (around Puigcerda) but only down in the valley on that side of the border. There are certainly areas there promoted as good walking spots. Again, May may be a bit too early for mountain walks.

• The Caminito del Rey, near Malaga in Andalucía, used to be a high-adrenaline/high-risk path, but it seems that it has been tamed.

Sorry that I can't help more. I'm basically a city walker.

Thanks info will be very helpful.

As well as the (several routes of the) Camino de Santiago, other popular walking areas of Spain are in the mountains - Pyrenees, Picos de Europa, Sierra Nevada.

This is an excellent article.
http://www.independent.co.uk/travel/europe/spains-classic-walking-routes-from-the-camino-de-santiago-to-rugged-pyrenean-routes-10516539.html

I was thinking some of the more gentle parts of the Camino would be fun for you too. You can have your bag shipped ahead each day to the pension where you want to overnight. Only costs 5-6 €. That is what a lot of people do who are walking the Camino. Especially those with back problems or those in their 70's, 80's, 90's. Yes, lots of older seniors walking this.

Given your time frame I would probably consider 4/5 nights in 3 different locations.
1. You really can't go walking in Spain and not include at least a short section of the Camino.
2. Walks around Grazalema, a white hill town in Andalusia.
http://www.andalucia.com/environment/protect/grazalema-walks.htm
3. Walks around Pallafrugel, a stunning location on Catalunya' Costa Brava.
http://visitpalafrugell.cat/en/routes/hiking/from-cala-pedrosa-to-aigua-xelida/

Thanks everyone for great advice.