We prefer to hike on our own, so I am not interested in tours offered by agencies in Hanoi or Sapa.
Unfortunately I can't find any information about hiking routes, maps or safety. Have you gone hiking in Sapa without a guide?
Thank you for answers.
Mentioned in this answer:
the mountain trail in Sapa Vietnam is rather dangerous, especially for people have never come to Sapa. So in my opinion i think you should consider to book a tour with trekking program like this : http://www.vietnamtour.com.vn/vietnam-tours/tour-styles/vietnam-trekking-tours/sapa-unique-3-days-4-nights, you will follow a local guide that very good at English and known the trail through every corner of Sapa, it's safer and you can require any break whenever you want.