Most likely the duck Roadblock must be after the mud Detour in Vietnam. That's why the people doing the Roadblock already look dirty.
Awesome preview of the first episode!
I'm a little worried about the music editing though; it was kind of strangely mixed in that preview.
And if there IS anyone going home on Leg 1 after Eric & Lisa, it would have to be an invisible team. It's a non-elim.