Laws are different in different countries. If you want the protection of the law in case of interference disputes (something that TV broadcasters typically have) registering your wireless is imperative. If you are touring and firing up as you go, this can be a problem because I think the registration process pins you to a specific location.
The guys at Lectrosonics and Audio-Technica have "wireless helper" departments staffed by people who are there to help you figure out the best solutions. Why not give them a call?