I am an entrepreneur in San Francisco and am afraid to tell people about my business idea without ensuring that I'm legally protected first.
When you have an idea, the idea itself seems incredibly valuable and a common fear is that someone else will jump on it before you do.
In my experience though, especially after multiple startups, the more you look around the more ideas you can find that - while not perfect - are certainly good enough to launch a business from. Without solid execution, however, they have no value other than engaging dinner table speculation.
Share your ideas. If they're deep enough to build a business around, the time you've spent thinking about them will be more than valuable enough for someone serious about execution to not try to cut you out of the deal. If they're trivially copied then they probably don't have much value compared to the massive amount of work it'll take to launch and sustain the venture around them.
Sorry if that's not what you're looking to hear, but I'd say that the NDA dance at this stage will turn off more people (especially investors who hear lots of pitches and can't afford an inadvertent "you stole my idea" accusation when they go with an alternate pitch six months later) than they're worth to you.