I received my packet today.
On the booking request form it does say at the bottom: "The Promoter and TLC give no guarantee that the hotels will be available for your preferred stay dates."
I called a CSR to ask about putting overlapping dates- e.g. mon tues for choice 1 and tues wed for choice 2. She said no, but I am going to try it on one of my choices.
I am submitting for April 2008 in Washington DC. All of the hotels are nice Marriott properties; I just do not want to end up on a weekend. (My vacation runs from April 12-20th).