Interesting you should ask. I'm not sure what the other region did but the NE conference now has a dress code. Clean coats and checks or black pants. Dress for business all other times. For evening functions, the dress is usually stated in the program and depends on the type of event.
Most conventions have at least one casual evening.
Dress for the national Chef Professionalism Dinner and for the Chef of the Year Dinner is always black tie. I have never felt unwelcome at any convention event because of the way I was dressed. There have been times when the best I could do was a blazer and attended the formal Chef of the Year dinner. The most important thing about convention is fraternity, followed by education, followed by participation. I got a censors message.