I think I should actually plant something for them to find so they'll think they really won $500. And maybe make the phrase something really offensive that they won't want to say. Or something that insults them. Like, "I'm a fat cow who has never exercised a day in her life!" But get them really excited about winning. Make them shout things, do dances, etc. Maybe say, "I'll give you an extra $50 each time you scream I JUST WON $500 from KPLA as loud as you can."
Those pay phones I found in Corvallis (15 minutes from me) are perfect. They're Qwest pay phones and they ring forever without stopping to give me a computer tone. They also ring loudly. And there's plenty of parking right in front of them, where I can place my camera. I was thinking I should tell them that the message is on TOP of the phone booth and see what they'll do to try and climb on top.