Yes, you can. MEX-BT5000/BT5100/BT5700U / XAV-70BT/E70BT allows one cell phone and one Bluetooth Audio device to be connected at the same time. When you make a call while your Bluetooth Audio is playing, the Bluetooth Audio will be dropped and allow you will be able to talk over the phone.
After ending the call, the Bluetooth Audio will start playing again.
Note that during your phone call the Bluetooth Audio will continue playback as normal but will not be streamed to the speakers.
This means that the Bluetooth audio device will not stop and then resume playback.