We've never been during Spring Break, but we spent Thanksgiving week of 2003, 2004, and 2005 at WDW. Each time we arrived the Sat before and left the Sat after. It was more crowded than we expected in 2003, and threw us for a loop at MK on a Sun. But we adjusted , learned to use fastpass, etc and enjoyed it. 2004 & 05 crowds were about the same but we were prepared for it. That being said, it was crowded BUT very manageable. Each trip was great. Our school system now gives us a week long break in Oct and that's when we went in '06 and back in '07.