I'm not aware of anything canonical for Vegas...
Hmmmmm... it's primarily marketed as a gambling city where you can "win it big". That points towards Mammon, the Demon Prince of Greed, having a major presence there.
It's also marketed as a place to come and see the floor shows - music, stage magic, and so on. That gives a reason for both Nybbas, Demon Prince of the Media, and Eli, Archangel of Creation, to like the city. (Doubly so in Nybbas' case, since the marketing itself supports the Media.) Some of those floor shows are "adult" in nature, which brings in Andrealphaus, Demon Prince of Lust.
Like many large cities in the US southwest, it's a small patch of greenery in the middle of a desert. Novalis, Archangel of Flowers, may have a small presence in Vegas.
Putting all of that together... this version of the
In Nomine Las Vegas is definitely in the Infernal camp, but not completely so. The Superiors who have an interest in the city tend to avoid violence, so it isn't a physical battlefront between Heaven and Hell; instead, it's a place where subtler Celestials can work to good effect.
(And feel free to use my
Impudite of Lust who's often seen in Vegas, as an NPC...)