You've definitely picked some great spots to hit. I haven't spent much time in LA or Chicago, and it's been a very long time since I've been to New York, but I've spent a little time in Vegas and New Orleans in the not so distant past. Vegas itself is a great spot for night photography, especially city scapes. The main strip is always full of life. I've always been there on other business and haven't had anything more than a point and shoot on me, but one place not so far from Vegas I went last time I was out there was Death Valley. If you're into landscape photography, that might be a good place to hit as well.
For New Orleans, the French Quarter is a treasure trove of photographic opportunities. The bad news is, you're probably not going to get a shot that hasn't been done before, but between the street performers, rustic buildings and year round nightlife, you can't miss. I haven't been there since Hurricane Katrina hit, but that may afford some unique opportunities in and of itself.