Most people do not look at small, unobtrusive cinder block buildings as attractive locations for restaurants. Dive bars, porn shops, other places you might not want people to see into from the outside, yes. But restaurants? Generally they are fairly well-lit and you have windows. Not Penny's.
This little hole-in-the-wall in Mint Hill (not South Park, as the map would suggest) is a bit of a puzzle. For starters, the building does not match up to the service in any way. Walk inside and you will see what I mean. You are greeted warmly and welcomed like one of the family. Maybe better than many families.
Beyond that, I really could not tell you when they are open. I think they are open for breakfast and lunch most days. But since it is so hard to tell when they are open because of that little building, I have to go by the number of cars outside. You need to figure out how to park there, too, since there is not much in the way of a lot - it might be easier to park elsewhere and walk across the street.
Should you manage to get there, the service is excellent (excepting the paper plates - that is a minor inconvenience) and the food is solid all around.