When is it a good idea to operate from an LLC and have them sign an NDA? Small project, but you never know. Personal use ATM, but that could change. I think them being local would dissuade them profiting from my idea. That being said, you never know if they're lying about their location.
Whether to bother with having an NDA obviously depends on the sensitivity of the material you wish remains undisclosed.
However, another aspect is whether you actually have the means and will to legally pursue anyone who breaches it. If not, the NDA becomes more symbolic - which might perhaps still be worthwhile.