That´s some useful information for you. At that frequency the communication is basically line of sight. The potential range of a pair of those devices does not mean anything if the path is blocked. That´s why it would be good to try scheduled contacts between the members just to find out who will be able to make contact. If you cannot use relais stations, terrain will have a huge impact.
With 70cm amateur radio I had situations where I could communicate at 100 miles with good ratings from a mountain top while not being able to properly pick up transmissions from about half a mile away.