Sit on the fence

To decide to avoid making a decision one way or another.

Girl 1: You coming to the movie with us?
Girl 2: No, she's coming to the club with us!
Girl 3: Umm, I need to think about this, I don't really want to have to choose.
Girl 1: She's just trying to sit on the fence.

by ZMan June 24, 2010