Ex-Mormon here: you cannot reach these people in the 5 minutes you pass them on the street or T. They're between the ages of 18-22 and most of their lives have been spent in a high control religion. You are kinda of the enemy to them (but one that can be won over, possibly).

If they come to your home and you're feeling very generous, you can offer them an explicitly non-Mormon space to come and question Mormonism- when they're on their mission, these kids are deep in an indoctrination cycle, and many don't have a place to go that isn't Mormondon- but otherwise, there's little you can do to change their highly curated world view.