I'm just off the Jewel on 07/31/2010.. yes people wore shorts in the Main Dinning Room.. I would only suggest that they look somewhat decent.. no bathing suits or tank tops. I used the MDR once and found it nice, but really took to TZARS which is in the ships stern and has a fantastic view. Guests wore suits, casual clothes and yes, shorts, but everyone appeard to be tasefully dressed when casual.