If you want to get to Agnew Meadows or Reds Meadow, you can take the shuttle from the Mammoth Ski Area. But if there is still snow on the road or the ski season still on (like it was for us by the end of June), you have to hike all the way up for five miles. It sounds worse than it is, because you will enjoy stunning views of the Sierra Nevada. Time almost flies.
During the busy but short summer season only the shuttle bus can use this road during the daytime, making it a relative quiet but certainly more gradual climb out of the valley to Mammoth, and certainly easier when there's still snow on the trails early in the season.