According to an online index of the markets etc there:
There is also a night market (J13 on the map)where Thai, Lao, Burmese
and local items can be found; starts daily at 8pm.
Here is a link to the map - sorry, I couldn't really convert it into a format here easily without pilfering it directly - if you find a way, feel free to update.
I don't think you are in Yunnan Province anymore. The only Jincheng I can find (晋城) is in Shanxi Province (山西).
In a similar question, I linked the Chinese version of the popular Western website Yelp, called Dianping. For reference, the Dianping site for Jincheng is: http://www.dianping.com/jincheng
Unfortunately, no one is really using Dianping in ...