I would Strongly Reccommend Chiclana de la Frontera, only 15 Minutes from Cadiz, only 1 hour from Seville, 2 and a half hours to Madrid. Plus you are only 15 minutes from some of the best beaches along the whole coast of Spain, not overcrowded, very clean and very very nice!
If you want more info, prrivate msg me and i wil be happy to explain in more detail.