We had a great stay here. Arrived to find clear instructions posted on how to choose and register for a site. Lots 1 & 2 are the grassy area right at the front, Lot 3 is just up the hill and is small, fenced in and paved. We never did see a Lot 4, but Lot 5 is at the top of the hill near the dump station. It is large gravel and probably the most level of the options. We chose the grass for our dog and he loved it.
There is a bit of road noise in this grassy area but it was warm so we slept with AC on and hardly noticed it. The town of Mariposa has a great supermarket, gas station and a quaint downtown. You are ~an hour to the Yosemite gate and about 80 minutes to Yosemite Village. The drive into the park is along the Merced River which was gorgeous when we visited.
We didn't need to use campground facilities but they are a short walk away. We appreciated that they watered the grass to keep it green and soft, was very pleasant for sitting out in the evenings. A great stay would highly recommend!