Each Ren faire has its own policies. Each Ren faire has an administrative body and public relations contact person. Some Ren faires are much more rigid and theme oriented than others. Just get in touch with the people running the one you participate in. If you are at a complete loss, start with your local chamber of commerce and they should be able to steer you in the right direction.
Never played whistle at a Ren Faire…Not possible to justify a whistle with the local powers that be. Sure did have fun with the hammer dulcimer, however… If we spoke, we had to use Elizabethan dialect - something with which I was never totally conversant… My solution was to outfit myself as a mute monk. Worked for me…
Cheers and good luck.
Byll