I'm also tempted to suggest that if the person doesn't see a cart on the C concourse around the elevator/escalators, I'd take the direct airside route to G that goes through the back of the parking ramp and then look for carts at the far end of G. I really hate having to run through the area of the main concourse between C and F/G when it's crowded and people are stopping in their path to window shop. At worst, G has reasonably wide moving walkways as does the C to G connector (although often there's one that isn't operating) so you can run faster on this route.