If you are looking for onsite stay, check the codes page on this site. There are some discounts listed there. Are you an annual pass holder? Discounts for that as well.
I think the most important thing is to book something ASAP so you have a place to sleep. You will be in the thick of prime Spring Break/Easter week. I'd get a room and then work on getting a better room or a deal from what others can tell you here.
Looking at mousesavers is a good idea. You might also want to check the home page of www.wdwinfo.com and see what Pete has posted.