Is the noise you get a AC cycle hum or a higher harmonic artifact like a buzz?
Ferrite bead on the guitars hot jack?
When I was playing out I went so far as to shield pickup cavities and pickup coils with copper, grounded. This does have a small negative effect on the tone of most pickups.
How many clubs have neon signs so close to the stage as to cause unbearable noise from sensitive transducers? It happens, but I don't remember it being a constant problem.