Hola! I don't know specifically about language schools, but it sounds like you and I are kind of thinking along the same lines. I'm graduating this May also with a secondary ed and Spanish degree, and I studied in Madrid in the fall of 02 and I absolutely loved it.
So, my goal is to figure out a legal way to go back and work or study for a year or so. I'm actually going to be in Avila from April until the beginning of July in a secondary school teaching English through a program at my college here. I'm getting graduate school credit for it; it's not a paid job or anything. But my plan is to check out the opportunities in Madrid and the surrounding area while I'm in the country in the spring, and then hopefully head back next fall, in September or October.
I don't know about the language schools, but I'm looking into taking some courses at a university in Madrid and then teaching on the side to support myself somewhat....does anybody have any advice or experience with the university system in Spain?? Let me know.
Carrie