This Johnny Rockets its located in the MGM food court. Its more of a fast food place, as opposed to other Johnny Rockets where you are served at your table. Here is more like a McDonald's, you place you order at the cashier, retrieve your food and seat at the food court tables along with people eating from all the other fast foods joints.
They are a little too busy during breakfast, so you might have to wait a little for your food, but nothing beyond reason. As a matter of fact, you can order from their breakfast menu throughout the day. And since you are in Vegas, they serve alcoholic shakes.
People working here are friendly enough, and the prices are fair. To be honest, if you are on a budget, you can avoid the expensive hotel restaurants and eat at the food court every now and then.