Hi Gerard,
Housing is easy to come by, plenty available currently, but it is quite expensive. I imagine housing will be included in your package, if not you will need to look at your package very carefully as housing can be more than most expats make!
The expat community in Pom is quite large and very friendly, there are many restaurants, clubs, bars and other social places to relax, enjoy a beverage or a meal and unwind. There is always events going on as well that include balls, degustation dinners and social night. Also there are many sports events and teams - squash, sailing, diving, fishing, tennis, gyms, kite surfing and more.
In terms of escaping for a day or two there are places you can do this. Koitaki Club at Sogeri is quite popular, and easy as a day trip or you can camp or rent a cabin. Some people go to Black Rock at Gaba Gaba and camp (mainly kite surfers) or Hula as well.
If possible you can request your potential employer to bring you to Port Moresby for a few days so you can see for yourself what it is like. I think you will find it can be a great place to live and work if you.