Where can I find a spanish language copy of the rules of Settlers of Catan.
Would this would be of any use to you?

http://www.yoda.arachsys.com/siedler/siedler_espanol.pdf

Failing that, this looks pretty thorough:

http://boardgamegeek.com/filepage/30216/catan-todo-en-uno-reglas-y-mapas-para-todas-las-ve