Penny I have one thermostat on my coach,when you turn it on you select what ever you want to use. If you want the heat pump on the front air conditioner, you select zone 2 and select the temperature you want. Your front heat pump will start in one minute and gradually will heat up. If you also want the rear heat pump also, you then select zone 1, and do the same as you done for the front. Now if you want furnace , select on the mode (furnace) and the only thing that will work is the furnace.
And if you want air conditioning then you select cool and set the temp.
I hope it is not that cold in Las Vegas, I will be there for two weeks during the Christmas holiday. But if it is that cold you will need the furnace, heat pumps are only good to around 30 degrees then the furnace should cut in automaticly.