We got to lava beds and were the only car in the visitor center parking lot. After getting the guide that noted the closed caved (due to bats) we took off down the Cave Loop road to visit some of the developed caves. First stop: Thunderbolt.
Most of the developed caves are only developed in the sense that they have ladders. No lighting or warning signs to point you the right way once you get in.
One direction (towards Labarynth, I think) was closed for bats, but the other direction was open.