How do I localize menu items added to the Main menu by a views page? I have a multilingual site setup where the pages in the Main menu are all created by Views. Main Menu is configured to 'Translate and Localize.'

When clicking 'edit' for a menu item the 'Translate' tab does not appear in the top right hand corner when the Language selection box is set to Language Neutral.

(This, however, does appear when I change the language selection in the drop down box to something specific; however, I want to Localize, not create a translation set.)

I know I have done this before. What am I missing? Note I am using node translation (content translation) and not entity translation.
If I understand your question correctly:

Go to Structure > Menu > List links
Assign the correct language to the link and then you can add a translation for the term.

One of your languages is to be set as the source language for translation. As far as I know a language neutral entity (menu, node, whatever) can not have a translated counterpart, because there is no source language for translation available.

Hope this helps.