Dress code for Florida? It's not up North, you know!
Canadian Dress code, particularly Ontario, would tend to be very proper.
If you look too proper in Florida, they will get suspicious! No kidding, thats how those 911 chaps presented themselves; clean shaven, shirt and tie, etc.
General Aviation District Office - don't worry, they are not interviewing you for a job. They just want to see all the paperwork in order. (And perhaps avoid dark glasses!) So be relaxed, and enjoy meeting them, they are airminded friendly guys. Share your plans and hopes, if they are not too busy. And it is possible to look smart in shorts, unless you are British and your legs are the colour of celery stalks......