You are never too old. I started back when I was 39 and my first ride was 2.5 miles and I literally was ready to bail (read that as DIE) at one mile. I now have ridden up to 60 miles and want to do a full 100 mile ride this year.

Some early advice is DON'T GIVE UP!! I almost gave up when I reached my 10 mile mark and my 30 mile mark on rides and the more time I spent riding the more I started to enjoy it. Don't worry how many people pass you, are faster than you, climb hills better than you, or say to you. Learn to enjoy the ride and then you will WANT to ride more and farther. This is a great forum to ask anything you want and get lots of help and "been there done that" stories to help you along your way. Just keep riding.