To become sober in terms of abstaining from alcohol, drugs, and/or any other commonly addictive behavior. It does not literally mean one moves to Prescott, AZ.
Prescott, AZ is recognized as one of the largest 'sober' communities in the Unites States, and possibly the world.
1: Is ToddRandy coming out to the bar with us tonight?
2: Nah, he moved to Prescott, remember?
1: (sigh)...sucks for him.