I have gone the week before the one you mentioned every year for the past 4 years. The lines are somewhat long, but nothing at all like the holidays. Then again, the first 2 weeks of march are the most popular spring break weeks and apparently some grade schools do spring break now (mine never did!). Anyways, the week you mentioned may not be as bad since it's after that major rush.
Sidenote, I've been to Disney at almost every time of the year at some point in my 23 years. The best time I ever spent there was in middle of May, before the grade schools get out. We literally walked on everything. Our longest way was maybe 10 minutes if that. I wish I had stuck to going at the time but unfortunately my fam's time share is in March and July.