Can you tell me if we should book restaurants before we get out to vegas or if we can just find a good one while we're there?

Because of the casino action, it's easier to get a table at the last minute at a rated resturant in Vegas than it is in say NYC or LA. That said, I'm a foodie and always reserve in advance to assure that I don't end up waiting in some buffet line. I just make sure that I pick resturants in the vicinity of casinos that interest me.

It depends on when you are going. If you are going on a holiday weekend, as we just did for Memorial Day, or plan on eating at some of the better restaurants, then making a reservation makes sense.
For instance, if you plan on eating at somewhere like Le Cirque in Bellagio, then definately make a reservation. But, on most nights, for most restaurants, especially if it during the week, you probably can just wing it.

Getting a table at 8:00 might require a wait, but after 9:30, it should be fine.

Your post suggests a willingness to reserve before arrival, so go with that initiative. Experience has shown me that some of the better restaurants are difficult to access if you wait. High end, high quality restaurants are in abundance in LV, so if you have an idea on where/what you want, make an advance reservation. If upon arrival, something else piques your interest and is available, cancel your first.. Bring patience, tolerance and check any bad attitudes at the airport, and you'll have a great time in LV. Enjoy your trip!

we always book before we go there.why wait and then be turned down and the good busy places will turn you down!