You have the option to hide the sentence that says, "Yes, please include me in the ACCOUNT_NAME mailing list" during the public checkout experience.

Head to your Public Display Settings >> >> Web Design Tools >> Fonts and CSS Styles.

Then, copy the code below and paste it into your CSS. 
 

.opt_in_div {     display: none; } 

Make sure you scroll to the bottom of the page and click "Update".

Now, start a mock order and when you get to the final checkout page (from the public view), check to see if the sentence is hidden.