Maybe it's just me - I grew up at the Royal Aircraft Establishment where it was clearly understood that if you wanted to be taken seriously, you wore a suit, and that is generally still the view in the aerospace engineering industry that the SBAC show is all about.
So me, I'd wear a suit, yes. I'm not going this year, but that has always been my custom and practice there, at Helitech, and at Paris. The same view seems to be taken by most of the other aviation grown-ups.
Corporate polo shirts are probably the next best thing if you don't mind being taken for a lab-tech or scientist.
A quick google only found one photograph of people going into the trade show. It does seem to support my opinion, the only person I can see in the shot not wearing a suit is selling programmes...
G