There seems to be a consensus on one point:
"You would have to ask them how they would prefer to communicate with you"
"Hmmm... ask them what method of communication do they prefer?"
"Well the Deaf should choose how to communicate"
"How have the employees been communicating prior to your arrival? Do they have any suggestions?"
It might be a good idea to have a sit-down meeting (using an interpreter) to clear the air about this issue, and find out what would work best for the employees and you.
