First of all, not everyone interprets the religion the same way. Some consider it haram, some don't.
There's not much you can do here to change others. To your friends who already know your beliefs, you may remind them that you wish they would stop.
Other than that, you cannot tell others to stop playing their music.
I've travelled in a lot of buses in India, and in most of them, they play some crappy song, which I find irritating not for religious reasons but, because I hate the song.
I do try and ask the conductor if he could reduce the volume, and sometimes they do reduce it for me.
Even if the persons around you are of the same religion, their dedication to following the religion may be different. As you said, theyThey might know that it's haram, but do it anyway. Bringing, or they might not even consider it up toharam. Telling them that the religion does not allow it will most likely backfire on you, and they will think that you're acting like you're better than them.
(edit: I don't know for sure whether music is haram, and I'm not taking any sides on that matter.)