Loved wondering around this fascinating market. Didn't have trouble with taking photos of people. Though some waved no and we complied with that.
We stayed overnight so wandered around the market while it was being set up and much quieter.
As someone mentioned, be careful of being ripped off with coffee and nuts etc. It happened to some of our friends too.
We also visited the Can Cau market further up towards the Chinese Border - even better than Bac Ha.
You do get hassled at both markets to buy bags etc, which we did, but it was all good fun. Much preferred to buy from these markets than in a shop. Items very authentic.More