No, the Cobblestone does not take up Wi-Fi bandwidth.
It's true that the Cobblestone may be on the same Wi-Fi channel as some of your other devices. However, even though its signal strength may be greater than that of say, your router, this does not mean that it is taking up Wi-Fi bandwidth. It may help to think of it like walkie-talkies on the same channel. One walk-talkie's signal may be very strong but if someone isn't talking on it, it does not disrupt other walkie-talkies on that channel. Similarly, the Cobblestone, when not in use, only sends beacons from time to time that announce its presence, and it is not actually taking up wi-fi bandwidth on that channel.
That said, our plan here at MUZO is to add the option to disable the Wi-Fi hotspot in the future. Please stay tuned for this!