I don't know how old to learn is, but I'm giving it a try too. I'm mid 60ties...
I believe there is one member that is 70.. Several have made remarks of deciding to try learning guitar at there old age or re-learning from many years away... I'm just learning for myself because I love guitars and if someone taps a foot in time that's great too..
Good Luck with the new venture and keep on a pickin'