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.
It's great to have an idea that you are passionate about. And most entrepreneurs wouldn't start a venture in the first place unless they were convinced their idea would be a success.
So it's a pretty common to worry about someone stealing your idea. In fact that fear can paralyze you to the point of inactivity.
And THAT is what you should be most fearful about.
Instead of worrying about the theft of your idea (which is, in my experience, very unlikely - people tend to be opportunistic and don't steal untested / unproven ideas - no matter how seemingly amazing the potential. They DO steal unprotected proven business models, but that's what I call a high-class problem) focus on executing.
Find reputable people to work with (experienced and ethical people whose reputation depends upon others being able to trust bringing ideas to them). And get your idea out there so your market can decide if they agree with you (about how great the idea is).
Build a MVP / prototype. Put together several business models. Discover your market. Develop your message. Create a USP. Craft an irresistible offer. Make some sales - lots of them.
If your idea and the business model you use are viable you'll have something worth protecting. Until then you're just someone with an idea - not an entrepreneur.
And by the way - Unless you have a ton of cash to spend defending your "idea" once you put it "out there" you probably can't prevent it's theft anyway. So the only way to truly protect it is to keep it hidden away forever.