Google is not going to integrate Google Translate service into Google+ instead they released Google Translate for Google+ Chrome extension which is available for download from Chrome web store. This extension translates Google + posts & comments in other languages to English.

Google Translate for Google Plus

Using Google Translate for Google+

Download and install this extension for Chrome, refresh Google+ page if you’re already signed –in. Translate button appears under for non-English posts, click Translate button and translated text will be shown highlighted.  You can revert back to original text by clicking Show Original button under the post.

translated comments