Ryan,
The fact that your getting television interference says it all. To me, it sounds like they are using frequencies that are not supposed to be used. You could get in serious trouble. Go to the A.T. website and look for the available frequencies in your area. You do this by typing in your zip code. You can also email A.T. I have always found them to be very responsive. I have 12 A.T. 3000 units and 4 of those are in the "I" range 482- 507 Mhz and they have been rock solid.
Also, if you need to get the receivers up in the air, go to Walmart and get a cheap bookcase and put some of the units one the top couple of shelves and put the thing against the wall just off stage, for $50 bucks they are up where they belong. Or, get some boards and a couple of shelving brackets. For $30, a couple of screws, and a 1/2 hour of your time you are good to go.
Lastly, as said before, don't be responsible for someone else's crap.
scott