The best time to book is when you see a great deal, as it may not be there the next time you search, but i think you first have to determine what a great deal is... have you researched prices (use our sister site MAPS and HOTELS.com); i'm seeing 5 star casino properties in the $300 area, so looking for a 50% discount over a weekend may be a bit of a reach given it's not ultra-slow season (if you're not aware you have a 50K person convention that ends the day before you arrive and some may stay a day later... and a 78K person convention the day after you leave and some may come early).
If you're not looking for any 5 star hotel (casino, lively, etc) i think you're likely looking more in the $200 area than the $150 area. Nobody can say if prices will come down, or move higher, between now and your trip, but rates in Vegas more more quickly than any other place in the country, which is why when you do see a good deal you need to be ready to grab it.
Our RateDrop service will monitor rates for your specific dates from both PRICELINE, HOTWIRE, as well as we 'regular retail rates' (if/when the regular rate at a hotel that you're interested in drops in price, it would be a good time to immediately do your search again to see if 'opaque' rates have dropped as well)
Please remember to return to BetterBidding and use the PRICELINE and HOTWIRE links on the board to begin your travel purchases... or thru our sister site MAPSandHOTELS.com for your regular rate purchases.
Let us know how you'd like to proceed and we'll take it from there.