Do Priceline bid option -- select the highest star hotel option, pick riverwalk/downtown location, and start at $100 per night. Nothing to lose.
If you go 5/4 star, most (if not all) of those are going to be nice area -- riverwalk and/or right next to it. If bid isn't accepted, then you can increase bid and/or lower star rating. So now you'd be at 4 star level, but don't bid more. Nothing to lose.
Don't be intimidated by Priceline if you've never done it. Perfect situation is you know the area you are wanting to stay and the dates. If you run out of bid options (basically nothing accepted for the lowball amount you enter - 24 hour hiatus before able to rebid), then just try again the next day. Always start really lower dollar amount and highest star rating, then work your way up.
For $200/night, you should DEFINITELY get a 5 or 4 star hotel. Just need to be methodical about slowly raising bid price.