I went for years and always found Allentown to be a lot of fun and worthwhile. However, now it's a bit far from Florida. I miss it.
I disagree with prrhorseshoecurve. You should plan your trip or day to do what you enjoy. Real trains may or may not be on the list. Obviously, you are going to a train show because you enjoy it. I wasn't aware of the Farmers Market (right on the grounds -- a really short walk) for years. But if you go on Saturday, walk across the parking lot, have a great lunch, enjoy the Farmers Market, and return to the train show totally rejuvenated.