Instead of a Cruz or Trump bumper sticker, which would nonetheless be OK, get a conservative bumper sticker, or better yet, tape a cover of Hayeks "Road To Serfdom" on your door. I guarantee you some of the intellectually curious kids, will wonder about it more than you think, and it will have more effect.
I remember being young in college and thinking socialism might not be so bad. That was before I read Solzhenitsyn's Gulag trilogy which should be mandatory reading in college. For the teaching staff as well.
Of course, many of these young skulls full of mush will change their thinking when they encounter the real world. But many more can be influenced now by an eloquent person in the Oval Office.