My guess is that Adventureland itself probably does not open until 10 AM that day, which would mean that you can not access that area at all until after the 'rope drop' at 10 AM. So, no... you would not be able to reach the fast pass machines prior to then.
Sometimes the MK opens in stages, with most 'lands' open at park opening... but others (usually Adventureland and Mickey's ToonTown, IME) opening about an hour or so later. Those later areas are kept roped off until their official opening time for the day.