We can't risk you running into your older self.
2 seconds sound clip from the Back to the Future Part II movie soundboard.
You can hear this line at 00:30:30.100 in the Blu-ray version of the movie.
Quote context
[...]
- All right, Einie, let's find Jennifer.
- I don't believe it. I live in Hilldale? This is great! Way to go, McFly.
- Marty, stay here. Just change clothes. If I need you, I'll holler.
- Come on, Doc, I wanna check out my house.
- We can't risk you running into your older self.
- Come on, Einie, let's go. Where's Jennifer? Where's Jennifer?
- One, seven, four point five zero.
- Here.
- I'd be careful, old timer. This is a rough neighborhood.
[...]