1) Joining the Army Rangers will not get you onto the HLA campus, it will get you sent to Iraq. The Army Rangers property does not back up to HLA's property, it is 2 miles away.
2) Walking right up is not an option either. It is 1 mile off of a public road and they have security guards at night and staff during the day who will question your intentions.
3) Hiking from the AT is possible, but once again staff will spot you.
Feel free to do what you want, but these options will get you nowhere except arrested for trespassing.