Yeah, it's the overflow hose. Actually, I think it's more of a vent hose, since it doesn't appear to be pressurized, and only vents after the pressure cap starts to open.

You'll have to remove the right front fender liner to access the overflow tank and the other end of the hose. Bunch of screws, takes a little maneuvering around the tire. I can't remember if there were any special tricks or not - it's been a couple years since I replaced mine.