I went to Vegas in April
Spent about $20 per night on accommodation (Circus Circus) with about $100 hotel fees on top of that. Then I had about $700 (£500ish) to spend. But if you want a proper good time e.g. Canyon, Helicopter tours you might want to double that. But for a drinking holiday it should be fine. Notify your bank that you're going on holiday before and if you do need some money take some out with your debit card. You might have a small charge and a limit per day but it'll get you out of any troubles.
Enjoy!