Most of the audience were University of Idaho or Washington State students. Before RP arrived they amused themselves batting around red and blue RP balloons, waving their signs, shouting, clapping and chanting, and singing the Idaho fight song.
There were many tables set up where you could register to vote or change to Republican. The two other people who addressed the crowd emphasized to them that they needed to attend caucus to make any kind of difference.
And, yes, there was standing room only in the ballroom. In fact, most of the people were standing because the organizers hadn't set up nearly enough chairs.