I just returned from a backpacking trip in NM and I would suggest that while you are walking try to condition yourself so you can walk 2 miles in 1/2 hour. Maybe walk 1 1/2miles at a normal pace and then pick up the pace for 2 miles. Then the remaining 1 1/2 miles can be done at your normal pace. As you get comfortable with the pace, add some additional weight to your backpack.

Good Luck

Chris