Personally, I'm not particularly excited about such events. I got into dancing because it was a "social" thing (i.e., I get to hold the girl's hand).
I've also never been a fan of dance competitions or dance performances. I mean, why would I want to sit down and watch *someone else* dance while the music's telling me to get onto the dance floor? (well, tap dancing would be my exception).
Of course, there are bands around with good reputations for swing dancing music (such as Eight To The Bar and The Love Dogs with their legions of fans) and I try to list them as often as possible if there's even a hint of dancing available. However, Some of them will play in small bars in some remote hick town that I'm not familiar with and I won't know if there's even a dance floor. In those cases, I will err on the side of optimism and hope for the best.
If the venue is a restaurant providing dinner music, go there and suggest that it'd be in their best interest to clear some space for a dance floor. The sight of people dancing could be an attraction for their customers and give diners something to watch while the band is playing.