It is your first amendment right to record a public event. Never let them convince you to turn off the camera again. If they do not want to speak on camera tell them it is their right not to speak but it is your right to record and report as you are representing the right to free press and in the age of the internet anyone can be a news source. If the reps do not want to speak on camera remind them that this is a town hall a public forum where they are addressing their constituents and they should be reporting to all of them even those not present. Notes are usually taken and you are doing nothing different then the note takers in the room.
Even better tell them you will be reporting this news story on a public forum for the people to see and point them here should they care to read the story and be involved in conversation around it. I would love to see some of the reps come on this forum and talk to us.
not sure about Or. but in Wa. I believe that you can video someone in public but no sound can be recorded.