When I get on google+ it asks me each time if I want to increase local storage and allow google+ 10mb more on my iPad. Does it need that much more?
How are you accessing it? I get to google plus via Safari on my iPad and have never seen this message.
I got this message on my iPhone 3GS. I think it stores emails, attachments and photos in a cache. I said yes.
I just log into google and click the google + tab in the upper left corner.