yep...dress shorts allowed. As are semi-non-dress shorts. Guess I'd say don't wear cut-offs, short-shorts or athletic shorts. No tank-tops on the guys. You'd be completely comfortable in knee-length shorts & golf shirts.
We have seen everything from completely dressed up (suit & tie on the guy, cocktail dress on the woman...to khakis & golf shirt on the guy & sundress on the woman...to cargo/khaki shorts, clean t-shirt and shorts/tank top on the woman.) Last time we were in Yachtsman (Fall 2010) I'd say 1/2 the people were definitely in Theme-Park-casual attire. Most of the rest of them fell into the sundress/khaki slacks category...only one couple really dressed up and they were celebrating either an engagement or an anniversary.
Citrico's at Gr. Floridian seemed to be a little dressier...more 1/3 theme park casual, 1/3 sundress/khaki and 1/3 suits/dresses.