How do you leave a review on the Google Play Store without a Google+ account?
Sadly at present, you cannot. Since around November 2012 Google require Google Plus to review on the play store. All reviews are in your name, have your G+ picture and are publicly shared.
There is a popup that states:

From now on, reviews you write will be posted publicly using your Google+ name and picture.
Your name on previous reviews will appear as &quot;A Google User&quot;.