yeah the gal that runs my local "pit bull" rescue is a lawyer as well. and she explains this about sinage at her training classes. her advice is a sign like G said "no tresspassing" or one that simply states "dog on property". nothing about beware or anything sounding like the dog is viscious.
Do not dwell on the past, you will not find your future in your rearview mirror.
If you mess with one dog, you get the whole damn pack!