I think it's a good idea to mention it as well, as it might become a point much later on.
For example, when I first decided to try polyamory, I was single. There were a few people who were interested in me, and I told all of them before anything even remotely went down that I considered myself polyamorous now. Nothing came out of those people, because they couldn't handle that caveat. I don't regret that, and in fact I'm thankful for it, because if I hadn't mentioned it and let it come up later in the relationship, things could have ended up a lot more dramatic, and people a lot more hurt.