Totally open. My daughter acts as my sounding board when I'm working on a plot, and she used to watch the show with me when she was a teenager. Not only do all my family and friends know I'm a FoLC, that I write fanfic, and that I've won awards for the same, but I make references to my fanfic writing in class (since I'm a writing teacher), and I've occasionally used examples from L&C to explain something we're discussing in class. Besides, in my office I have two Dean Cain movie posters, two pics of me with Dean, and several Superman pics. Several of my non-FoLC friends have read my fanfic. I don't think I've ever mentioned it at church, but everyone else knows I'm an L&C/Superman/Dean Cain fan.
