Yumthang Valley is in North Sikkim.
Yumthang is 140 km from Gangtok. 1 night 2 days and 2 night 3 days packages are available from Gangtok. Route 1 (Yumthang-Katao-Yumesamdong) Gangtok 24 km, Phensang, 16 km, Phodong, 30 km.
Route 2 (Lachen-Chopta-Gurudongmar) Gangtok 100 km, Chungthang 26 km, Lachen 30 km (3 hr) Chopta Valley.
The roads are not in a good condition. You will have to hire private vehicle from Sikkim and need permission beforehand to visit Yumthang.
There are several small coffee shops run by local inhabitants serving tea, coffee and breads. The coffee is worth trying.