The Tryp Diana is nice; I have had lunch at their restaurant El Pato Mudo (the mute duck) and it was OK. But with as short a layover as you have, have you thought about Barajas Pueblo?? On the Square (Plaza there's a Churreria that's frequented by many airline crews: It's called Toribio's and I believe it's open from about 05:00 to noon (or thereabouts). There's a city bus that passes the airport and terminates there (M-101?) but it probably won't be running that early.

The Plaza is kind of like a small park complete with wooden benches to stretch out (or whatever). I had a 4-hour layover there once from about 07:00, called some friends & relatives and we all met at Toribio's for Churros con Chocolate. They also have very good Cafe con Leche, Churros and Porras.