The 2 best buffets are at Paris and Bellagio. The "play" is to arrive near the close of breakfast hours and pay the cheaper breakfast price - then chow down on the lunch selections as they convert the offerings. These 2 are extremly tasty well pepared and presented with mucho offerings. About $12.
The Stage Deli in the Caesar's Forum Shops is the real thing. Try the chopped liver.
No first hand experience but the Liberty/White Cross Drug Store on S Las Vegas Blvd south of Stratosphere and across from Olympic Gardens Mens Club has a 24 hour counter that is supposed to be the best all night breakfast. Have read several sources on this. Will post more as I recall them.
I subscribe to the Las Vegas Advisor which specializes in finding great bargains. Quantity/Quality/Value puts something in their monthly Top Ten Value List. 2 that have been there for a long time and that I can vouch for are a $4.95 steak dinner at the Ellis Island coffee shop and the $1.99 burger at Wild Wild West Casino. Both are 24 hour operations and these taste best late night. These are "locals" places.
A good frozen custard is at Luv-It Frozen Custard on Oakley, just east of the strip south of downtown.
The Original Pancake House has at least 2 locations. This is a chain which grew from Walker Bros Pancakes north of Chicago (and probably on the Roadfood listings). The Dutch Apple Baby and Lemon something are their signature dishes and will fill you up just fine.
In 'N Out and Fatburger have multiple locations.
Your biggest problem may be that you will be up near the Speedway and most everything else is a long way from there.
Will post more as I can remember.