For $39.99 there is an all day buffet pass at the Luxor/Excalibur (both buffets). The Luxor buffet was very good and the Excalibur was just okay, in my opinion. But the lines were never long and you can stop in as many times as you want during the day. I think it goes from 7:00 AM to 10:00 or 11:00pm. We stopped in a few times, just to get a pop or a snack, as well as for our normal meals.
Harrah's buffet is pretty decent and not badly priced.
The Bellagio's buffet is Excellent, and if you get there before lunch ends, you get the lunch price. Just sit, relax, take your time, and enjoy some of the dinner entrees, as they bring them out later. The Bellagio is worth it, even if you pay the dinner price, but it is pricy.
They have several In & Out burger locations in the strip area too. The nice thing about them, is they are not badly priced. You can get a meal for around $7. Since I don't have In & Out by me, it is nice to go there a few times, when in Vegas.
Are you doing the bus pass (the Deuce)? This last trip we did the bus pass and it was really worth it, $20 for 3 days. The busses come every 20-25 minutes and go up and down the strip and to the downtown area. The downtown area has better priced quick meals, like slices of pizza and stuff like that. I have not heard any good things about the buffets down there, but I have not been to them either.
Stay away from some of the quick meals on the strip. We once stopped for a piece of pizza (on the strip area), which ended up being pretty lousy, with a soda, it was just under $15. For a few dollars more, we could have gone to a decent lunch buffet or somewhere nicer. The quick food on the strip, is not worth the price, to me.