Minimum age is 18. I don't recall the statue number, but I am sure of it. As far as backpacking goes, in CO you can legally concealed carry if you are hunting, so just by a small game tag and you can concealed carry because you are "coyote hunting".
No Denver, schools (I think its w/in 500 feet), anyplace where federal employees work, and anyplace thats posted.
Have fun and remember to watch out for those big kitty cats we got over here!