Three things about the LS.
First, there is no reliable way to discern a swinger from a vanilla without someone asking/telling. This is one reason why swinger resorts exist. Someone has to ask. No means no. No thank you means no. Maybe means no. Yes means yes. Get used to a great deal of no. Occasionally nudists will bristle, but that's the exception--they know that running around naked is an alternate lifestyle, and there is some overlap among the lifestyles. See the third item.
Second, naked does not imply LS even in a nudist environment. Many nudists are just that, G-rated nudists. Their conduct would pass muster at a church social--except for the nakedness.
Third, some nudists eventually do cross over to "the dark side" and join the LS. We were/are in that group. Swinging is out of the question until it's situational. And then it's no longer out of the question.