The big attraction there for non-cave, OW divers is the ballroom. It’s a large cavern with a guideline that goes to 45ft and has a main spring access in the lower right portion of the main room. There are also smaller areas to check out, especially in the upper left portion of the ballroom, which can be cramped.
The Devil’s cave system is non-accessible to OW divers, though there are cavern entrances to the devil’s ear and eye. The ear especially has a cool cavern that is reasonably roomy. From there you can often see cave divers passing by as they continue through the cave system.
As DiverMikeB stated, the dive center does technically specify no lights or lines. You don’t really need one for the ballroom, though it’s very nice to have.
The nicest way I’ve found to dive the system as an OW diver is to start at the "little devil" entrance ramp and swim down the narrow channel to the devil’s eye. Drop down into the eye for a quick look, then come back up and hop over to the ear. This is the cavern that’s nicest to see cave divers passing. The flow is very high at the entrance, and you need to be careful not to get blown out and hit something when passing through. After you come back out of the ear, swim up the river (with the current) on the left side and you’ll eventually run into the side channel to the ballroom. You should still have enough air on one tank to be able to go into the ballroom for a few minutes and explore. I usually just stay at the ballroom for my 2nd tank and hang out. Since it’s only 45ft at the deepest point you can get about an hr on one tank.
Wish I could come on the 21st but I’ll be working that night. Have fun!