I treat them them as tropicals... for now all of mine are in containers in a cool greenhouse... tender, warm and happy!
I'm still experimenting with hardiness of these Nelita variants.
You could grow them up a bit, harden them off to cooler temps and set them out in a protected area like the south side of a building or windbreak.
My Run-of-the-Mill Cherry of the Rio Grandes (not Nelita) seem to have quite a bit of hardiness in a protected area with temps even down to the lower 20s in containers... should fare better in the ground in a similar area.
Here's a topic on COTRG hardiness you may find interesting:
http://tropicalfruitforum.com/index.php?topic=42322.0Kevin
Kevin