In May, 1999, I hiked around Hetch Hetchy Reservoir to Tiltill Valley with Robert, Kim,
Donna, and Debbie. This is the best time of the year to visit Hetch Hetchy, as the
temperatures are (hopefully) subdued, but plenty of water remains in the waterfalls and
streams.
Go here for a trip report
which seems to piss off most people here in the Bay Area.