I've tried the tip found athttp://misteratmisis.com/infotech/how-change-oracle-sql-developer-interface-japanese-english, namely adding the VM options
(Tested with SQL Developer 17.2.0.188)
Edit file at
/Applications/SQLDeveloper.app/Contents/Resources/sqldeveloper/sqldeveloper/bin/sqldeveloper.conf
and add the line
AddVMOption -Duser.language=en
