Getting ripped off in Zhongshan is understandable, I have been in China more than three years and still get ripped off from time to time. It annoys me of course and I used to tell my Chinese students my misadventures in China. They told me this is normal and that since I am clearly not from around there, people will try to take advantage of me and that next time I should go with a Chinese friend. I have since learned how to deal with these business men and women as best I can and I think it boils down to knowing the prices and how to bargain in Chinese. They will usually try to get a better deal from you if you do not look like you are from there. Actually many of my students told me they also get ripped off because they are not very familiar with the area either. Know the area or at least have a friend with you know does if you don't want to get ripped off too much.
Be very careful to hold your purse or bag in front of you. And do not wear your backpack on your back, always wear it in front of you. It happens a lot that someone will ride past you on a motorbike and try to steal you bag, as they think you are rich and unaware because you are a foreigner.