From Dallas your looking at about 14 hrs to Denver. However you might want to think about the Pecos Wilderness in north central New Mexico, very similar to areas of CO (altitude, etc) and only about 10 hrs. It's a great place to backpack.
And I was just kiddin' about TX, one of the things I do like about livin' here is you can backpack from Oct to May...well, I do in SW AR, and no snow to shovel. June thru Sept, better for hitting the mountains or heading up north.
Good luck with things in Dallas, and come join us in a hang sometime.