RESOLVED with your assist, Psy, thanks.

• Checked for the file you referenced but I did not find it at the directory cited at site https://en.bitcoin.it/wiki/Running_Bitcoin (/Users/username/Library/Application Support/Bitcoin/bitcoin.conf)
• As the file did not exist, I created it and entered only the language setting code you provided.  On restart the Bitcoin-Qt application was in English
  
• In conclusion it appears that without an explicit statement from the bitcoin.conf file, the application simply defaults to the system's original language