There are two distinct Costas of the coast of light. They are divided by the Donana Park which runs alongside the great Quadalquivir River. When the Spanish were conquering the Americas, much of the new found riches would be brought up this river to Seville. The eastern Costa de la Luz runs from the mouth of this river to Algeciras near Gibraltar. Much of the coastline is 'undeveloped' except for the area around Cadiz Bay. The beaches and towns around the Bay are popular in summer months and El Puerto de Santa Maria is very popular for its many restaurants and night venues and is a very good base for exploring the area . Of course, this is the Atlantic and you will have tides and even surf sometimes ! Winters tend to be quite mild except for a very few weeks of cold but the summers can be sun sun sun.
Down towards the south you will find Cape Trafalgar which is popular for summer holidays and just a few miles inland is Vejer de la Frontera - a really typical 'white town' , very popular nowadays with foreigners.