I had a little trouble finding the Centre Diosecain and hotel Urumuli. When you get dropped by the bus on the main parking in the centre, it’s another half an hour walk further along the same road. There are some motors in the parking, but I found it hard to explain to them where I wanted to go.
When you want to visit the tea factory, which I can recommend, a tour inside is possible. Going there by public transport, first take a bus from Byumba to Rucomo and from there take another bus in the direction of Maya, near Uganda. Ask the driver to let you out at the tea estate, about 12 km from Rucomo. There will be a few motors waiting there, but the walk up the hill is also pleasant.
Hotel Urumuli is nice, but overpriced in my opinion, charging 50 USD for a simple room.