I purchase the inexpensive metal wreath hangers, then hang an approriate wreath on my resort room door as well as a few decorations in the window. I never use tape or markers of any kind. Mostly clings or other cute things on the window ledge. I also take window cleaner and clean the window upon my leaving. So far the rooms I have stayed in have metal doors.
I get metal hangers because they are very thin, I bend the hanger around the wreath for stability and to discourage sticky fingers. I know we are in Disney, but there are still those who would like to ruin our fun.
I also try to keep my decorations within the holiday or the already theme of the resort. For example we are staying at POFQ, so my wreath and decorations are Mardi Gras theme for our June 2011 trip.
Hope I have helped.