I am founding a movement in the US (LET'S GET GLOBAL, Crossing Borders, Sharing Lives) to encourage young people to do a gap year (international experience) after high school and before college. This slogan would be great for us to sell to help fund the promotion of our idea and to help kids earn money for their travel. We would put our name on the back.
I know that slogans cannot be copyrighted....but this is a matter of a unique juxtaposition of two slogans. Can I get into trouble if I make up thousands of these shirts, thus copying someone else's idea? I can change a few words ("But we really should start seeing other people."), but the idea is unique. It's so perfect for our message!! We would put our name on the back along with the words of the slogan.