Hola Profe Hugh,
I've gone ceramics shopping several times in Bisbal but have never gone beyond the main street with its many, many shops. There's a museum there, but I don't know if it's the type of thing you're looking for; I think it covers industrial ceramics. (In catalan:
http://www.labisbal.info/terracotta/ )
Will you be anywhere else in Spain? Because I can highly recommend seeing the ceramics in Talavera and nearby Puente del Arzobispo. They're on the road to Portugal from Madrid. Talavera is a bigger town and is full of fascinating ceramics factories. I was there once with some friends and after just asking in a shop, we were ushered into the factory, which was an unforgettable experience. Puente del Arzobispo is a small town that lives on the ceramics industry. They apparently have 47 factories - and it's small! You can simply ask to see them work.