No matter how prepared you are there are always going to be times when unforeseen circumstances prevent you from being on time. For me personally this would have to be the most stressful part of photography. All you can really do is be early. In my books two hours early is better then five minutes late. Be punctual! By doing this you give your self a chance to get a lay of the land, assess the light, talk to the people. Everyone is an insider! You never know what tips you can get from that old guy in the corner that has lived there for 50 years.
Luckily on this trip i had my web designer Sammy driving and with his unrivaled knowledge of the CBD we mad it on time.