Sometimes it's nice to find adventures close by. Enjoy sweeping views of the Bay Area, camp above 2,500 feet within an hour of downtown San Francisco, and beat the crowds to the summit the Bay Area's highest mountain!
The camping
Start by visiting the Reserve California website to see if Juniper campground on Mount Diablo is available for the dates you want. It's $30 a night, which isn't the cheapest rate, but the amenities are top notch, with large sites, ample drinking water, flush toilets, showers, fire pits, picnic tables, etc.
It is first-come, first-serve (regardless of what your emailed permit says), so it pays to get there a little bit early. Sites 11, 13, and 15 probably have the best views, and offer some privacy and seclusion.
Regardless of where you camp, walk over to the open space towards the end of the loop road for sunset. It's a truly remarkable view of the Bay Area, ranging from the South Bay, the skyscrapers of San Francisco, up to the peaks in Marin, and north across the Delta. The park gates close at sunset, so camping inside the park is the only way to get these views!
Note that the park is a "dry" park, but be smart and you should be fine...
The hiking
It is said that the view from the summit is topped only by that of Mount Kilimanjaro in terms of the amount of the Earth's surface one can see. With binoculars, Yosemite's Half Dome is even visible from Mt. Diablo.
If that's not enough to sell you, it's only 1.5 miles from Juniper campground to the top of the mountain. Start early enough and you'll beat all the crowds - the park gates don't open until 8am.
The trailhead is at the exit from the campground loop road. You can't miss it.
Once on the trail, there is a fork about 0.2 miles in - stay on the Juniper / Summit trail (go right). From there, the trail continues upward, crosses the road once, and then puts you in the summit parking lot. Continue the rest of the way to the observatory at the summit.
It's just under 1,000 vertical feet from the campground to the summit, so while short the trail is pretty steep!
Enjoy the views, and then head back down!
We couldn't see Half Dome, but we could see the snow-covered Sierras in the distance. Truly remarkable - enjoy!