As the other responder noted, what maps or data (restaurants, hotels, sites, roads) are shown would depend entirely on the software application you use. I don't know but would guess that China might be more restrictive than some countries on data and gps use. So you clearly would have to do some inquiries.
There are two programs that might help although not necessarily with turn-by-turn or vocal instructions. Trekbuddy and MobileGMaps (NOT google) both allow you to compile maps on your computer and load them to the BB. Then the gps would spot you on those maps and you could navigate like the old days using the map and your location. Now, again, does China have mapping data of the cities or areas where you will be online?