Serena,
My guess is, if you are a weekly stay, like a time-share week, it will not matter what day you actually arrive. You will most likely be assigned a unit on the rotation of the week you have booked.
This will mean that you will be assigned a unit in a building color coded in BLUE. It is usually hard to get Cascades or Lakes (the newest). ALL of Courts (the oldest) is designated BLUE for a Sat-Sat week. (Check out the interactive map on the Starwoodvo.com web site)
If you have any request, you should contact their Diamond Lane check-in system well before your trip.
Good Luck!