Best location to retire without a vehicle

So long as you keep away from the countryside you shouldn't have any problem with transport either around the town you choose or between that town and others.

For instance we lived in Cartagena, about 200,000 population, and the buses around town run till 11pm at night and go basically anywhere in the city. Links from there to the regional capital were fast, cheap and regular. Several trains and buses per day to Madrid, Barcelona and major destinations.

i live in the middle of nowhere but I'm going to Valencia today by train. I'm going to the town of Petrer to catch the train. I think Petrer is about 50,000 pop (though I could be way out) they have buses around town too and there were five or six trains to and five or six trains from Valencia for me to choose from through the day.

Our town (pop 8,000) has a couple of buses going to nearby towns but they are so infrequent that I have never been able to make use of any of them even as an "adventure"

Barcelona and surrounding area has excellent public transport with metro, buses and trams. It is a small compact city with just about everything you could want and you can access other cities in Spain and outlying towns using the excellent overland rail services. I often travel between Alicante and Barcelona by the high speed train and choose it over the plane every time unless I am in a real hurry.  All means of public transport are cheap however the only downside I have found is the steps on the metro however the city is improving accessibility with lifts and escalators. Hope this helps.

Thank you to both of you for this information. Appreciated.

We would like to rent a small car for one month in Torrevieja.
Does anyone know a cheap place for rental's car ? Thank you.