If you stay downtown and really live cheap, you can get away with $1,000 minimum for a week. That's $700 for the room (avg $100 per night) and $300 for food and gambling (about $40 per day).
Don't forget to add $30 per night to any advertised room price. A $60 per night room is actually $100 per night with resort fee and tax. They fool you with that. Unless you go super budget like Motel6.