I live in Carlton but was an OSP engineer for Verizon. My travels took me all over their territory. Over near the REI store and Bridgeport Village there are a ton of coyotes. Mostly around the river and the railroad tracks. They come into the local neighborhoods at night and eat food out of the dog and cat dishes as well as the dogs and cats. I saw one a while back over in Sherwood happily trotting down the road near the YMCA with a dead cat in it's mouth. I would imagine things aren't much different in Portland proper since there are so many wooded areas.
What I would do is first contact the PPD and explain in detail what is is you intend to do and where you intend to do it. I'd explain that the pics are going to be used in an article on urban coyotes. That's been a hot topic here in the Northwest as you probably already know. Since it's Portland you may need some kind of permit but I doubt it. In the actual calling process I'd be more apt to use kitten sounds or coaxer sounds and at a low volume. I doubt that you'd be bringing them in from any great distance. I don't think I'd be using howling sounds as some whacko might think you're werewolf and come after you with silver bullets. lol
Over in the Forest Grove city limits, to the amazement of my wife, I've called in coyotes just by lip squeaking. Although there are lots of coyotes locally here in the Carlton area I've only shot one but I have called in dozens of them just for the fun of it. Too many hippie farmers and city transplants (liberals, tree huggers, antis) and houses that are just too close together to be safe.