Before I purchased my forty-acre observing site in San Benito County, I scouted many "dark sky" locations south of San Jose in San Benito and Monterey counties and further south.
I had been toying with the idea of buying a dark-sky site for many years, while engaging in amateur astronomy from so-so locations and with portable instruments. Then a note in an astronomy usenet-group pointed out that a firm was selling off old no-longer-needed microwave relay towers. I looked at the website of American Tower: sure enough they were selling some of their sites. None of the ones for sale, though, was suited for astronomy and near me. But that sparked my interest in radio-tower sites: as the note had pointed out, they are often in dark locations, and they come with road-access, power, and communications -- although you do have an antenna in your sky.
So I called up American Tower and asked them it they would consider a "co-locate" at an existing location, where "co-locate" meant, not adding a transmitter and antenna, but adding a small observatory on a concrete pad. Their reply was approximately "It is novel for us, but we are in business. If the site is suitable, we'll create a pad and lease it." And so I began checking out microwave-relay locations in the boonies.
I eventually bought my own site, but I did visit -- and observe from -- a number of interesting antenna sites south of San Jose. Locations included the coast range just east of Carmel Valley, the San Benito Mountain massif, the Temblor Range southwest of Lost Hills, and the summits of Williams Hill, just northeast of Lake San Antonio, the popular star-party location.
If you are persuing "dark sky" opportunities in the area south of San Jose, I would be happy to talk with you and fill you in on the opportunities that I found.
You can contact me via the information at the homepage