As far as the ringtone coming through the speaker...
If you have an android I'm pretty sure you can shut that off. Make the bluetooth connection only for music, not for phone calls. You'll find it in the bluetooth pairing settings.
I'm 100% positive you can prevent calls from going to the bluetooth speaker. I'm not 100% positive it will stop the ringtone from going to the speaker first. You'll have to test it.
If you are using a wire....whole different story. I don't think you can prevent calls from going out on the 3.5mm cable.