I have had the same question and what I finally did on my own when I dont want the radio on is I hit the music button till it moves over to the HDD tab which is your downloads that you have to select but dont auto play. from there you can go into the nav/pictures/menu screen so you dont have to look at the radio screen and use your uconnect when needed.

that is what i do. I'm on my phone all day for work and that has worked great for me.

Im sure there is another way but that was easiest for me for now.