It's hard for them to know exactly how good the Hong Kong public transit system is without being explicitly told, taking cabs is a natural choice for most foreigners in a new city. They also stated they knew there was probably a better way for the boarder crossing, but chose not to look since it was convenient and they didn't mind spending the money.
I'm pretty sure they knew the menus in China would be in Chinese, they were just stating the fact so the reader could understand that doing a simple task such as eating was actually a challenge to a foreigner.
It's not crazy to want to eat something familiar and safe. It's good to try new things which they did, but some times you just want to order something to fill you up that you know will taste decent. It takes awhile to figure out which local cuisines are delicious and which are a bit too foreign for westerners.
I do think that they should have been a bit more prepared, but they certainly did a lot better than most people who travel to China. The entire experience is quite a culture shock no matter how much you prepare.