You dont have a lot of options for nightlife in this area.
Dont try to leave your hotel's area because this is still a desert and you can fall or find a dangerous animal (leopard , snake).
You can enjoy in your hotel's lobby or sit outside and enjoy the desert silence.
Dress Code: The desert can be very cold place during the night so i think you should take warm clothes with you
The youth hostel at the base of Masada might not provide much "night life", but we found a fun life of our own when we met with Margozata (magor65) who came to visit Israel with a group from Poland. We met her and a few others in her group (you can see Margozata,me and her friend, and it does look like at least ONE of us was having a good time) and had a very fun few hours till we had to let them get some sleep before their climb to the peak of Masada. But take the time to enjoy the night sky in this area, less spoiled by the night lights of cities.
One thing that you wont find in this area is night life, people come to this area to rest, to treat their body an to relax.... nothing to do around at nights except for going down to the Lobby at the hotel to have some drinks, listen to some music and chat.