We have eaten at Mama Melrose, and Sci-Fi.
We enjoyed Sci-fi. After mixed reviews, I was nervous. We all got burgers, fries, and shakes. With a PS, we were seated in less than 5 minutes. I don;t think the whole meal took over 45-50 minutes.
Mama Melrose would be a longer meal, but very very good. Quiet, and a nice break from the parks. My DDs both fell alseep, in the AC, and DH, and I almost did too.
Counter service at MGM, gets very discouraging reviews, on these boards. I've only gotten a turkey leg there, and they are the same everywhere. Sorry I can't help with the fast food options.
Have fun on your trip.