In my area police run radar constantly while patrolling (driving). My detector has always warned me in plenty of time to slow down under these circumstances (usually I get a signal before the cruiser is visible). I have also picked up "instant on" radar and even laser and have not been pulled over while using my detector. For me, it works.
I use a Valentine One in the car and on the bike. I would recommend it if you are considering one.
There are a number of devices to help alert you on the bike above the wind and exhaust noise. Search around online. You'll find something that'll work for you.