I usually say I'm polyamorous, because most polyamorous people know the term, but otherwise yeah. I also live in Portland, and hang out with crowds where this is more common than normal. I did end up dating one monogamous girl, but she was completely okay with it - work occupied 90% of her life, and having a partner that didn't mind seeing her once or twice a month worked out very nicely for her.

I generally bring this up well before asking someone out, so that I can get a good feel for their reaction (often first or second meeting - just talking about my life makes it pretty clear I date multiple people. "Oh, today I hung out with girlfriend A and watched Farscape, then got a haircut with girlfriend B")

I also tend to emphasize my particular style of polyamory, which centers on honesty and the idea "It's not cheating if everyone involved has agreed to play by different rules". I've found signalling "I'm poly, NOT someone cheating on their spouse" is important :)