Yes, there is a little shortcut from the Liberty Arcade into Frontierland, avoiding the main entrance to that land. However, you can't use this to get into this part of the park before the rope drop. At busy times of the year (and possibly other times) the main turnstyles open up to 30 minutes before the official opening time. You can walk up to the end of Main Street, but not into the other lands each of which has a couple of Cast Members blocking off the walkways with a rope. At 9am the ropes are 'dropped' (the infamous 'Space Mountain Rope Drop Sprint') and you are free to enter the rest of the park. The Liberty Arcade/Frontierland cut-through has its own rope drop along with other areas.
If you follow the walkway from the Liberty Arcade/Frontierland cut-through this will take you along a covered walkway (more or less continuously) through Adventureland and into the back of Fantasyland (coming out by Peter Pan). Useful for inclement weather.
The only other shortcut is the occasionally open road from Discoveryland to Fantasyland. This is only open for part of the day, as it is used for a staging area for the parade floats. It goes from Star Tours to Small World.
Regards
Rob
