Yep! I did 5 miles on my old TREK mountain bike last week, trying out a walking/biking path at a local park. Went back with one of my road bikes this week and did 10 miles.
I have been off the bikes for about a year or more mostly, recuperating from a couple of injuries - first, a broken kneecap, then a sprained rotator cuff. And once you pass that magical 60-year mark, it seems like you don't bounce back from those injuries so fast.
I used to not like riding on MUPs - I always found them to be boring, and I worry about the walkers with dogs on leashes and coming up behind folks using their music players - but I tried this MUP at a county rec department park near my home and come to actually enjoy it. Unlike most of these trails, this one is very clean and well maintained, and has very few long boring straights. Lots of curves and little bridges to cross, and at only one point does it cross a road. It runs around the entire perimeter of the park, passing several baseball and soccer fields, and about 1/4 of the trail runs along the banks of the Ohio River. Total length is 1-1/4 miles.
Getting back in shape and hope to lose the 15 or 20 pounds that I picked up during my recuperation.