Cell service at Monarch is not very good. While this might be nice to escape the real world, it can be inconvenient.
There is no service in the lodge, or at the base area.
Your best bet for cell service is to ride Panorama or Garfield up to the top of the mountain. From on the ridge, you will get a strong signal. There are convenient picnic tables if you are planning a long call.
At least the view will be great while you talk.