In and Out
I'm a soon-to-be-single mom (my husband and I separated three years ago over my newly discovered poly nature, among many other issues). I've been a secondary with my married bf for over five years.
I am open and out with all my friends and family members. I am out with some of my clients (my personal life is not relevant to most clients--but my story is helpful to some of them....so just as some of them know I'm partially disabled, because it's meaningful to them, some know I am poly, because it's meaningful to them...it's not something I tell every client or announce on my website).
My 12 year old son knows and loves my bf very much. His school counselor knows, in case issues come up. His therapist knows, because my bf and I talked long and hard with the therapist before "coming out" to my son.
My bf and his wife are open with their friends. Bf's wife, with whom I do not have relationship, is more cautious professionally, so we are careful with that (our respective businesses sometimes intersect). My BF has not come out about me to his family, with whom he is not incredibly close--the ones he is especially close to are elderly and frail, and he doesn't see the point in rocking the boat or their world.
In general, we both maintain a policy of not hiding our relationship (we go out together, display PDA, he's got a wedding ring, I don't--I guess someone could do the math and maybe come up with the right answer, although I think an "affair" would be the more likely guess). But we also don't necessarily make big announcements. Like, to the neighbors: hi, this is my married boyfriend, he's in an open marriage, I know his wife, and it's okay, etc.
Both of us feel strongly that if directly asked, individually or together, we would respond honestly and authentically.
This may be "easier" for us than for some because we don't live together--I see my bf once or twice a month for an overnight or two. Eventually, because bf and wife are sort of gypsies--they love to travel and have lived all over the country--we'll probably go back to the long distance relationship we started out with, where we talked a few times a week and saw each other for 5-7 days about 3 or 4 times a year.