Carmona is very charming, but I agree with Puna. A week or two might be a lot. It sounds like you are looking for a small place to relax and not interested in doing much travelling. How about Cadiz? It has charm and is large enough to keep your interest, but small enough to be relaxed. (Do you like walks on the beach?) I have only done daytrips there, but really like it. If you want to daytrip from there, you have lots of options and good public transport.