On the 2nd day in Sapa we did a trek (7 hours, 16km) from Sapa via Y Linh Ho to Ta Van. It was just us two, the guide ("Shoe" who is from the H'Mong tribe) and 2 other H'Mong women (one had a baby as well). The 2 H'Mong women followed us because they wanted to sell handicrafts that they produced. At the end we bought some things and it was good that they were with us because at the beginning of the trek it was very slippery (rain the night before) and steep.
We walked on small trails that are used by the locals. Within the first 4 hours we saw just 2 other tourists. We can only recommend to take a trek like this without other people because the feeling you get from the area is a lot more intense.