I booked a three day trip to Sa Pa to do some trekking. On the first day we arrived early in the afternoon and hiked to the homestay where we would stay for the night. I was the only non Vietnamese guy there which was really awesome, because I got to experience the local customs first hand. My guide on the first Day was called Hoai, a really cheerful guy, who met the whole experience really pleasant. In the evening we had dinner with a local family where we had great food and a lot of rice wine. My favorite experience in Vietnam!
On the second day I had a guide for my own called Ni. She is a local so could tell me a lot about what it's like living there. I learned a lot. We hiked to the next homestay where I had great dinner as well.
Overall I can really recommend doing the 2 nights trip with APT Travel.