There is not any kind of marker designating your arrival to Mono Pass, you'll just know you've gotten there when the trail finally ceases going upward, and starts to flatten out and descend. There is one small wooden sign alerting visitors that no fires are allowed (though I don't know where you'd find any wood to burn!).
Mono Pass is a really cool place. There was probably once a much bigger lake in this area - the small Summit Lake being what remains. What is left is a lot of granite sand (decomposed granite, or DG for you civil engineering nerds!). Thus the trail is very soft and easy to walk in (though it is a bit like walking on the beach, and you sink in a bit).
The entire area is made up of "DG", and is in a bowl between Mt. Starr - a rubble pile of a mountain, and an unnamed pile of rubble on the other side. It really is a moonscape. The only thing that seems to grow are some scrubby sage brush and patches of wildflowers.
Congratulations, you've made it to 12,000 feet!