If your reason for attending a model railroad show is to research the hobby before you jump in, check out the work of the local clubs in the various scales. Some clubs are divided into sections which model similar scenes in different scales. Other clubs specialize in one scale or a particular scale and gauge.
Take time at a show to check out the interests of particular clubs and talk to members about the idiosyncrasies of working in their particular scale. It is possible to create very similar models in different scales, but HO scale for example has far more display pieces and buildings to base displays on than does N scale. Prices may vary widely from scale to scale as well, with smaller scales often commanding larger prices for detailed items.