You can learn a lot about China at HBA, but I think there are things you can preview before participating in the program. I did not do much preparation before HBA, and am regretting about that now. So I would like to write what I think should be done before attending HBA.
You should study about Chinese history. Beijing has a lot of historical places and historically important goods. If you know Chinese history, you can understand the meaning of these things and the importance of them. However, if you do not know about history, you do not really understand why they are important. For instance, when I went to a museum about China-Japan War, many exhibits emotionally hit me since I knew about the history of that war. However, when I went to National Museum and saw exhibits about ancient China, I could not understand the importance of them.
Knowledge of Chinese songs makes your life in China happier. I started to listen to Chinese songs several weeks after HBA began, but if I had started before HBA, I would have been able to talk about these songs with teachers from the beginning, or to sing these songs at karaoke.