With Las Vegas, plenty of good properties and if no major convention in town, the prices can terrific. But, the flipside is if there is a big convention in town. I'd do some searching now and place some price alerts on favoured places. MGM is good, Bellagio is wonderful. Aria and Wynn are good too. All upper end price wise. Mid-range, there is a Hilton Grand Suites just off the South boulevard which is fine. (I like it as its a non-casino property) I think MGM has one also close by.
New York, Manhattan is expensive. Get to Brooklyn. I'd have a look at Air BnB here. Some super places. But get in early. San Francisco, I've stayed at an awesome backpackers...(20 years ago) and The Argonaut, close to Fisherman's Wharf. Brilliant, but not cheap. (think $500+)
L.A. hmmm, mostly dreadful every place I've stayed....but sure others have super recommendations. Maybe try Air BnB again.
Good Luck