In Episode 1, Mike Peterson is sitting in a blue collar diner, reading the want-ads,
when Skye suddenly appears and sits down in his booth.
On the outside window of the diner is the name "Ruthie's Skillet".
Skye tells Mike that she knows his secret (that he was the unknown hero who rescued a
woman from a burning building), and tries to persuade him to use his powers as a hero.
She also warns him that S.H.I.E.L.D. will be coming after him.
When he gets up and leaves, she steals his driver's license and learns his name.
This scene was shot inside a real restaurant. But it's not named Ruthie's Skillet.
This is the "Spring Street Smoke House Barbecue", a Southern style rib joint
It's also close to another location from this episode: Union Station.
at 640 N. Spring Street, which is just northwest of L.A.'s historic Olvera Street,
and just east of Chinatown, in downtown Los Angeles,
(You'll find the restaurant's website here.)
Here is a Google StreetView of the location.
[ This same restaurant is seen again in Episode 20 (again as "Ruthie's Skillet")
in a scene where Ward & Skye spend some tense moments. ]