This depends on your budget, but it is advisable to hire an interpreter in the city where you are visiting. If you visit more than one city then you can even consider hiring a different one for each location, to save your travel costs. However, the advantage of using the same interpreter for the whole visit is consistency – saving you time in briefing each interpreter.
As a minimum, you should consider getting a one-page summary translated about your company, your product or service and your business track record. You can then post the same page on your website. Then you can make bullet points to put into a presentation format. For China, you need to make sure the Chinese characters used are simplified Chinese not traditional Chinese – traditional is only used in the territory of Hong Kong or in Taiwan.