You might see some towards the end of your stay. The MVMCP and Osbourn lights start on the 12th so those parks usually start decorating by then. During that time frame the resorts start to decorate so you might be able to see yours decorated before you leave. I know last year we arrived around the 10th/11th and SSR was decorated when we checked in and we went to the first MVMCP on the 12th and the park was decorated. Here's a pic:
But definately not all of the decorations. Sorry to say, but we have seen many decorations being installed after this timeframe. You still may get to see the beginning of the decorations.
And after MNSSHP on Oct 31st we went to Animal Kingdom. The park was decked out for Christmas. Characters dressed in holiday frocks and Christmas music playing. We went back to Magic Kingdom Nov 3rd and it too was decked for Christmas with the Christmas tree too!