A different thought
Everyone on here appears to be concerned whether the person they're looking to date is okay with their ring or not....would you really want to give the idea to anyone interested in you that you were single?
To me, the question is, what about outside parties? If you're on a date, and you're wearing a ring, and your partner isn't, it looks like you're cheating. Do you care about that? Possibly not, I'm not saying you should either way.
But to me, that should really be the only concern. Anyone you're dating, who has a problem with seeing the ring, probably isn't the best fit, anyway. Like the spouse with the date....his date has the right to know, from the start, that he's married, and he should really find out, from the start, if she can handle this (if she can't handle seeing evidence of another partner, is she really cut out for poly?). Why deceive her about it when you don't have to?