Do not let these turtles go, but for a different reason. We don't know what they were kept with since they were hatched, so we don't know if they could be carriers of a diseas (bacteria, virus, fungus, parasite) that could harm native turtles, fish, or predators/scavengers that could eat the turtles. Remember carriers can appear healthy but harbor a disease.
Also, they likely aren't native to your area, and although they originate from the south, they are a very hardy species that has become a pest in many parts of the world. They grow big, breed fast and often, and eat just about anything, so they can out-compete some native species for resources.
They do survive many different environments, from the northeastern US to Washington state, and even in Japan and England. That's part of the problem - they do too well in non-native areas. The original poster was right - they will revert back to a wild state pretty easily in most cases, and will hibernate naturally if they have enough time to acclimate to a new pond before winter sets in. That's called "feral" when a captive animal reverts back to a wild state. We have feral house cats in many urban areas of the US, feral farm pigs in the south, and feral sliders just about everywhere.
If you can find someone with a FENCED-IN backyard with at least a 300 gallon pond, and are sure that the turtles can't escape the yard, then you could let them go before September or October, but releasing them into anything other than a backyard enclosure could be breaking the law in many states, due to the risk of native wildlife and fisheries.
Katrina
