I live in Henderson 30 min away and photograph in Vegas a lot. I usually only carry my 24-105 f/4 L. Don't be obvious and don't look pro with a lot of equipment, otherwise the guards in buildings will chase you even if you are only photographing the interior architecture. And forget taking a tripod to use in buildings. I also would suggest you take a day or 2 and visit Death Valley. It is a cool spring and still not too hot right now, although that will soon change. I plan to head up there myself this weekend.

Don’t try to spin it as good advice. You were just being an ass. You could easily have just read the question and moved on if you had nothing decent to say. As a matter of fact, you could have just read the subject line and moved on. So it looks like you read the question already planning on belittling the OP. These questions are pretty common on here, and while I’m usually pretty sure what I want to take on any trip, I can understand the indecision of others. I also reject your conjecture that there’s no difference in shooting different cities or different mountains. There’s nothing wrong in asking people that might know an area better for advice. That’s what these forums are for. Whether or not you think the question is valid is no reason to treat the requestor with anything but kindness.

Having lived in Vegas and go there all the time and took a couple of photos there and with your 1 lens restriction of what you have I would take the 24-70.
But I own several lenses for a purpose and that is to use them.
An excellent setup would be a FF fisheye, your 16-35, the 100-400 is a must for Zion and get the 24-105 for the versatility that the 24-70 totally lacks.
Night shots work just fine with these lenses. F2.8 is worthless, it is not fast.
If you want fast take the 50mm as anything less than f1.8 is actually quite slow in real life.

Maybe it was a reason to start a conversation. Maybe they were looking for a second opinion. Personally, I tend to lean in your direction but the last time I said things similar to what you said, I was pretty much told to mind my own business.
By the way, even though you said, don't take this personally, the OP probably will, and justifiably so. In my response to the OP I made a suggestion that's not on the list. The Canon EF 28-300L is the one lens to take when you can, or want to, take only one. It is an excellent utility lens.

Las Vegas is an amazing city for both the horizontal and the vertical, but the scale there is just amazing for the huge hotels. But, taking pix of these buildings from the ground will cause the vertical lines of the buildings to converge, dramatically in many cases. If you are into architectural shooting, you might try to get your hands of a tilt-shift lens that allows you to bring those lines parallel, increasing the drama of the shot - while not having to backup too much.

I know that you can deal with these problems with post-processing in some software, but I like to do as much as I can with the camera right when I take the picture.

You can rent them for short periods, as well. If you know how to use them, they are also used for panoramas.

Please don't take this personally, more a general comment to lots of UHHers but every time I see a question like "I am going here and what lens should I take?", then they proceed to list a half dozen lens I always sit at my desk shaking my head in wonderment. First, why would someone buy all those lens if they don't know when and where to use them? And second, the world is not basically different from the aspect that mountains in another country or state will have the same opportunity as mountains next to your house. Water is water, no matter where it is located, street photography is street photography world-wide. Sure, dependent on location, photos may be more amazing or bland, but the equipment doesn't change. Leaving for a river cruise in Russia next week and I am 99.9% sure what I need to take along. Why don't others? (barring a very young, brand new photographer who doesn't have any experience)

You didn't say which camera you have. Obviously Canon, but which model?
If money isn't an object, I'd pick up an EF 28-300L. Actually I don't have to, already own one. If you only want to take 1 lens then that's the lens to take. A lot of people hate that lens and the majority of haters don't own one. Sure, it's not the fastest lens available but it's fast enough and it's sharp enough also. Canon don't make junk lenses, especially L series lenses that cost what that one does. And no, it is NOT a dust pumper...

Think this out, Las Vegas, has biiiiiiiiiiiiiiiiig buildings, fountains, more buildings and so on. I stayed at a hotel that is no longer on the strip, back in 2003. used a film camera at the time, you will find that no one lens will capture every thing. Lets break it down. the 24-70 mm is your best all around lens no matter where you are for most that you will shoot, the 16-35 mm limits you to all wide angle work, so if your using one lens, not enough range. The 50 mm is good if all you want to shoot is 50 mm, I would say NO! the 70-200 is good for the real long shots and it would be useful at Zion NP but as the only lens I would say no, not useful in Vegas. Toss the 100-400 unless you want to shoot wild life at Zion. If this is not a trip that you will do again any time soon, I would take the 24-70 and rent a 70-200 F-4, the F-4 is much lighter than your 70-200 F 2.8,will be easier to pack. I would also take a travel tripod. Jim M, New York.