we stayed at Vistana Resort through an exchange and they told us that there are specific units that are designated for certain check in-check out days ... For instance ( I'm guessing here) if you check in on Sunday you stay in the Springs section, Saturday - Cascades. If you go to their website there use to be a map and it was coded each day of the week was represented by a different color and that could give you some kind of idea as to where you may be placed. If all else fails ask when you get to the check in desk to be in a specific building . You can also go to the website and do Diamond Lane Check in (I recommend this if they still do it). It lets you put in your room requests.
I know that I should have checked their webiste prior to posting this info, but I didn't have the time......SORRY!