Having worked over the years for several American companies that do business in China, I have had numerous occasions to visit China with colleagues or to host them when I was living and working in Shanghai. One thing I have noticed few American business people actually try to learn some Chinese before they visit China. I can recall any number of colleagues who could not even say 你好 (ni hao) or hello when they landed in China.
My personal opinion is that it is not wise policy to go to China without a handful of Chinese words and expressions and at least skeletal knowledge of Chinese history and culture. The Chinese are very proud of their culture and many of them resent the fact that Western Culture, in particular American culture, is the dominant global culture. By speaking only English one projects prevailing attitudes in the West about Western vis a vis Chinese culture. I would add here that nowadays when China’s economy is pulling the world behind it, American arrogance – for that is how it is perceived when you travel to China and speak in English – seems slightly anachronistic.
By speaking Chinese, however, you pay deference to your Chinese hosts and this is something they will not forget. When a vendor has to prioritize orders the fact that you attempted to speak Chinese to him/her or praised an aspect of Chinese culture – like calligraphy – while one of your competitors failed to do this may mean that you get a better position in the production queue or that more care is taken loading your product onto the container. Of course, in most cases trying out a few phrases from your Lonely Planet China guide may not make much of a difference at all. But the point is, you never know. It does not hurt to make the best possible impression you can on your vendor. I would add that speaking Chinese while you are in China will make your visit much more enjoyable. If, on the other hand, you travel to China and cannot speak any Chinese you will experience a lot of frustration.
For this reason, I always encourage people before they go to China to take a Mandarin class. I think speaking Chinese is an indispensible part of doing business in China. As the Chinese say 入乡随俗.（ru xiang sui su） When in Rome do as the Romans, or in this case, When in China, do as the Chinese.