We stayed on a Thursday night in June at the Mammoth Cave Campground. We had a reservation, but there were several sites that were vacant. People arriving without a reservation wouldn't have had a problem finding a campsite. However, I would imagine that the campground is full on the summer weekends. The campground is close to the visitor's center, hotel, and store. The campground has flush toilets that were fairly clean. The pathway to the bathroom was lined with lights at night. The campground was mostly wooded and there was enough distance between sites. Our site was flat, as were all of the others. The campground was quiet at night. The only complaint that we have is that someone was smoking pot near our campsite. We felt that this was completely inappropriate since we had children traveling with us and so did most of the other campers. We never saw the campground host or knew where they were located otherwise we would have reported this camper.
The other lodging in the park didn't look so welcoming. We had no problem with yellow jackets, other insects, or animals while camping. We were happy with our decision to camp and will stay at this campground again the next time we visit Mammoth Cave.