I have done both, 2 way radios and cell phones, with the 2 way radios I never had a problem, however I always shut it off during a show and told my dh , if I don't answer is because I'm on a ride or in a show. I have the vibrate feature with the cell phone and guess what?? I couldn't tell when someone was calling because I didn't feel anything, so I had to keep it on ring but again , the phone was shut off during shows and during rides since most of them are loud , you can't hear it anyway.
I have verizon nationwide plan and I never paid roaming charges from anywhere in WDW , we also have free mobil to mobil , believe me it worked great!