It depends on the type of radio you use. In general the FRS radios (ones you don't need a license for) are good up to a max of 5 miles, although this is substantially reduce by buildings and such. We took them on our 2004 trip and frankly it was a waste. The only time I found the need to use them was right before a parade and my wife was hunting down a restroom with our youngest. I kept trying to let her know I had found a good spot but she could not make out what I was saying. We use text messaging on our cell phones now.