I like some aspects, but there are some bad points...
I like the way you do some of your furniture, and other small details, but the walls and parts of the roof are very spammy. You should try to either make it look like actual bricks, or use much bigger ones, to reduce brick count ... and make it look better.
The third screenshot seems so.. wide open and empty. My suggestion would have been to have two floors of cells, with a "balcony" overlooking the open space, and perhaps cells on both sides. -- This is based off the only jail I ever remember seeing on the inside, which was on a historical field trip, so you might look at actual pictures, and you might leave it the way it is.
The signs resting on the ground are unusual. I would have put them higher next to the door or above the door.
The guards' lounge's ceiling should be redone with larger plates, and the gun sitting on the ground next to the chair just seems out of place.
You have some typos on the menu. They're spelled watermelon - spinach - salad. Also, I don't know, but i don't think jails have ..menus.. :P
Ignoring the spamminess, it's better than some of my first builds, I'll give you that. What I like most is the picnic tables, I don't know why.
