It is always ok to take photos of children, unless they clearly refuse. For adults, always ask for permission. In the more remote Communities of Kapchorwa there is often a fear that the photos will be used for wrong purposes. Most people don’t know about the concept of tourism. Therefore it helps to explain why you came to visit the area. What also helps is to greet in the local language and invest some time in making a connections. Ugandans and Sebei people are (generally) very friendly and hospitable people who love to ask questions about your home country and share similarities and differences in lifestyle and daily activities.
In Mount Elgon region, the Communities of Sipi Falls are more used to tourists, while the Communities around Kapchorwa are more laid-back. In the Sipi Community you need to be sharp to not pay too much for tours, access to the falls or crafts.