At my previous job, I kept it mostly secret that I was taking up ballroom. Partly I was a self-conscious beginner, partly it was easier to say, "I have to go do something; I'll be back later tonight," than to say, "I'm leaving to go a dance class." It was a dying company, the team relationships were strained, and I'd been burned before by letting folks know details of my non-work life ("that's not more important than work").
I switched to another company. I put dancing on my resume, in the one-line "interests" section at the bottom. In my group, one person had danced before, another was just getting started, and a third has parents who dance and said he may get curious to try it, down the road. There's a champ-level dancer in another part of the company. Someone else who had recently departed the company, had actually been one of my fellow competitors in silver standard at a large local college comp.
The other guy in my group who danced, made himself known as a guy in our group who danced -- not as a guy who delivered results. I let people know that I do it, but talk about work while I'm at work and make sure I deliver what's expected. The one approach is definitely not as good as the other.