It's really not an easy answer. My characters were totally stuck on it as was their illustrious writer.
I decided to ask the audience. I kept the original question simple to get gut reactions and avoid giving too much away. It surprised me how many people responded throughout the different places I posed it.
On my facebook page, the consensus was unanimous that the characters should release the prisoners to create a distraction. I had a few suggestions that stated there may be an ally in the prison that could help my characters. This actually solves a problem for me as to how they escape the rest of the way, so I'm going with it.
Okay, so to answer the other questions posed. This will contain some spoilers, but here's the scenario:
The Two characters that are escaping are neutral good alignment. They both have strong morals and a code of honor. One is a warrior monk, the other is a wizard. They are armed, fit and healthy, but tired. Any extensive use of their abilities could put them out of commission.
They were exploring ancient ruins and discovered the city underground was still flourishing. They learned that a black dragon is in charge of the city and that there are slaves working underground ranches in massive caverns. (It's very different from the Underdark. There are no traditional fantasy races such as dark elves either)
Their (powerful) friends were captured and taken away. Just the two of them were left and they fell in battle. The monk woke up in captivity and overpowered her guard. She then saved the wizard (her husband) They have the keys and escaped the lower level of the prison. They just reached the main level with the other prisoners. They know nothing about the prisoners.
Here is the conversation they just had:
Teluith checked to see that Reben was ready. At his nod, she opened the door and stepped through, ready for a fight. Instead of guards as they expected, they entered into a long hallway with stone cell doors. The murmur of voices turned out to be prisoners speaking through food slots at the bottom of the doors.
Reben touched Teluith’s shoulder and gestured with his head for them to retreat into the room. Once the door was closed he whispered, “Do we help everyone to escape, or just sneak past?”
Teluith opened her mouth to answer, but conflicting thoughts interfered. “Are they in jail for bad crimes, or for trying to escape this place?”
Reben shrugged. “Both are possible. I don’t know the answer.”
“We should ask them, no?”
“Criminals tend to lie, my lovely. It would do no good.”
Now I just need to figure out who's in the cells and go from there.
It shall be fun.
