I've been there recently. Bottom line: Most visitors to the TDLR are Japanese. So as far as CM's go, not a lot of english is spoken. They do appear to understand more english than they can speak.
We stayed at a Disney (good neighbor) hotel. The hotel staff did not speak much, if any, english.
At TDL, you can get an english map at City Hall. All signs are in both japanese and english. Some attractions have english translation headsets, some (like Country Bears, are in both languages -- Blood on the Saddle in japanese is a hoot), and some are only in japanese.
Don't let language stop you. Disney Sea is not to be missed!