Can I go to Erhai lake by bus from Jade Emu Intrnational Youth Hostel or three pagoda?

Well, the lakes covers a large area, and I suggest you enjoy the beautiful scenery from Caicun Wharf, which is within walking distance to the lake.

You may take bus line C2 from Shuangshi Road Intersection (near Three Pagodas) or Honglongjing Station (near the hostel) to the wharf. Or directly take a taxi there with the fare of CNY15-20.