I heard that the crowds will not be to high since a lot of schools are not on spring break yet and it is a weekday. I hope it isnt crowded because we will be there.
One other thing to note is that even though it seems early for Spring Break, lots of Band and Orchestra and Choir, and dance and cheerleader groups go to Disneyland to perform or to festivals in So. Cal. and then go to Disneyland. When we were there last March (early in the month) we saw tons of school groups, so it wasn't un-crowded by any means. Lots of families tack on vacation when their kids are going to be there so they can see their kids perform and enjoy Disneyland, too. I would just plan on Spring-time being busy at DLR and then you won't be disappointed if it is.