My brother completed this on his bucket list. The taxi driver didn't have a clue where it was and I had to keep showing him on my phone. It was much quicker and cheaper going back to the 9-11 Memorial.
There is not a lot to do at the Stonewall NM, but the weather was perfect and we enjoyed sitting on a park bench, viewing the garden, the Inn, the signs, and especially the statue.
To my delight, the "rangers" set up a temporary visitor center, decorated the statue, and even provided the National Parks Passport cancellation.
The Inn itself served drinks only, no food, and didn't smell good, so we spent most of our time relaxing in the park.