You will be able to eat very cheaply in Vegas. Hotels have buffets (I don't know if Circus Circus still has the biggest buffet in the world). They want you to go there to gamble so cheap food is a very good incentive. You will have variety in everything and the usal burger joints and chains will be well represented.
Try the Luxor, went there in September and was exellent. Try to get there before 4pm as the price changes afterwards. Price wise I seem to remember that it was about $14.99. This all you can eat buffet really does have a good selection of food from around the world and will leave you fuelled up for a night of partying around Vegas