Yes, release it. But do take some pics.
Some turtle pics of what I've come across:
Adult box turtle
Baby box turtle
I think both were found (on different days) while I was mowing. The baby was darn lucky it wasn't run over.
The adult was very cautious and took several minutes before coming out of its shell, but once it did, it didn't seem overly concerned with being handled. The baby didn't seem to be fazed by anything.
Both were released after their photo sessions.
I also encountered a snapping turtle once. He was trying to cross the road at a pond near my house. Note: turtles aren't
always slow. Snappers can turn around pretty damn fast, and this guy was pissed off. He had his mouth wide open and came right for me. I was cautious about him though, and he never got so much as a nip of me. He was eventually persuaded to go off the road and toward the pond.