You can find Bac Ha on the right side of Lao Cai highland province, meanwhile Sapa is on the left. I was there on the first market of Spring time, also was the first Sunday market of year 2014. It's not only a market but also a culture (of the ethnic minorities of northern Vietnam). To know Bac Ha market in details, since it's worth a try, Google is the best tool. And since my words & my writing are limited, pictures instead can tell a lot in their own ways.
Enjoy & get insp