This is a nice, relatively short (15 minutes each way with slight uphill) walk, with a sampling of the typical Bryce red-rock pillars scenery. The "cave" itself is actually a slight overhang perhaps 30 feet wide with moss growing on a few spots. As such it isn't terribly exciting, though perhaps for somebody living in the southwest seeing that amount of moss anywhere is unusual.
Near the cave there is a bigger waterfall with a 20 foot drop that's on the river you follow along the walk. When we were there the overlook was closed for maintenance, but you could still see the waterfall from the trail. Some people followed the river to the waterfall and it was constantly populated with waders the 30 minutes or so we had lunch under a tree along the trail. I didn't go down there so I am not sure how powerful the current is in that location and I wouldn't immediately want you to think it might be a good place to take small children for a swim unless you checked with somebody first. There isn't a designated trail or swimming area.
The trail itself is out of the main part of the park and involves a 15 minute drive from the visitor center. I am not sure I would consider it worth a special trip if you've had a sampling of the real Bryce Park, but it could be something to include if you're east of the park anyway. The trail head is outside the gated area of the park so if you're not stopping at the main park but want to pick up a short hike on the way to/from Tropic this would be a way to get a small sample of the park scenery without going to the area where you have to pay a fee.
If you have children, one of the park's children activities is accumulating a certain amount of medallion hiking miles. I think this hike gets you 0.8 miles (check the park's web site for details). If you're heading into Bryce from the east you could stop here to get them started (take a photo of the participants with the special gold medallion signpost near the cave).
No drinking water but there was an outhouse.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.