Mmmmm the U.S. Egg is absolute greatness, what Denny's could be if it only tried a lot harder.
Get the protein pancakes. Even if you don't necessarily want protein pancakes at that time, get them, take them home, put em in the fridge and then eat small pieces of them throughout the day. They're absolutely wonderful. The Border skillet is also a winner--great chorizo and salsa. Have heard the Eggs Benedict are great.
Delightful place. Obviously fills up fast on weekend mornings but have never suffered through too long of a wait. Service has always been pleasant. Prices are reasonable enough.