Yes, for breakfast and lunch you can wear shorts in the dinning room. Just don't go into the dinning room in swim suits, ladies can put on a cover-up and some shorts and still get in there. Now, dinner is a different story all together, no shorts.
I was on the Grand twice last year....Shorts are the norm for breakfast and lunch, but I was surprised at how casual people dressed at dinner...and I did see a few in dress shorts, but there were also alot of people in jeans and t-shirts which really were not appropriate in the dining room
I second Cardow's statement. In March, the 83 yr. old gentleman from El Salvador wore regular casual Bermuda shorts to dinner on the last evening with a knit shirt at our Traditional Dining table. I was so surprised because he was a very refined gentleman. Guess he had packed everything else!