I would suggest not going with any preconceived ideas, as i did. My Project was teaching English at Ripa Siddhi Sangathan Monastery just outside of Pharping, which is approximately 25mins drive into the mountains from Kathmandu.
My stay at the Monastery was not what i expected, however I believe i got more out of the project than i gave.
I went for 5 weeks but it took a couple of weeks to settle into the routine. Be prepared for very basic plain meals of rice, dhaal and one seasonal vegetable with breakfast consisting of beans and bread. The Monastery itself was approximately a 25min walk to Pharping. The area is beautiful and the local people friendly. The staff at the Monastery, as well as the young monks are Nepalese, so the language coarse at the hostel would be an advantage. Classes in English were Monday to Wednesday, which gives you four days to organize site-seeing or trips into Kathmandu, with buses leaving regularly from Pharping. Be prepared for a lot of free time. The area has lots of temples and lots of walking opportunities and Pharping has cafes with WiFi and an internet place if you don't have your own computer. Be aware that your WiFi and internet depends on power, which often went off and apparently is worse in winter.
Staying at the hostel was also a great experience. The diversity of young people from all parts of the world was great and the staff were very accommodating and helpful. Don't hesitate to ask plenty of questions, as when you get here you will have plenty more you didn't consider.
If you are interested in this project feel free to contact me for more details.