You need waiver,

You are Permanent Resident of other country (Like Canada, France, UK), But you still need to write to Department of State to get a ADVISORY LETTER indicates that you are not subject to J1 two year home residence.

You are subject to J1 waiver if:

1. you are chinese (skill list between US and China)
2. you use Goverment money either from US or China
3. you get medical trainning in US