Been working here for a while and I do go to my neighborhood char chan teng often. My cantonese is half bake but they have been quite nice to me and can joke with me as well. As yes they can be rude like just putting the utensils down with a thud but its just because of the speed. So far I havent had really bad experience with really rude people but I know it does exist. Sit in a bus and you can hear people talking on the phone so loudly that you will know where he will be going for tea and with who.