I drove through Port Moresby at 5am in a van with a security guard and an Aussie miner. There were gangs of young guys carrying machetes at intersections just eyeing us up as we went past. The hotel I stayed in had razor wire and armed guards. It felt like I was in a war zone. Definitely didn't strike me as a good location for an international sports event.
PNG is a borderline failed state. I doubt anything bad will happen with these tournaments but the location is definitely not a pleasant or welcoming place.
I spend a lot of time in Port Moresby for work, and while we do travel escorted at night, during the day time the city is 'relatively' safe. Some of the comments above about fears of getting into really serious trouble are pretty much unfounded, yes its a violent place by western standards but the problems are mostly tribal and rarely directed at foreigners (unless you're a chinese business owner).
With that said I hate the place. I've also played football there, including a training session with Hekari United and it is a terrible place to play football, particularly during the daylight hours. It will be hotter, dustier and drier than Honiara.