Just went to San Francisco, Yosemite, Sequoia, and Tahoe during part of a two week California vacations in June.
San Francisco was awesome. We were there for about three days. Took a tour of Alcatraz, saw the Golden Gate, Baker Beach, Land's End, Golden Gate Park, Fisherman's Wharf, Lombard Street, Hilton Cityscape (great view of the city, especially at night), and took a tour of AT&T Park. Also got a personal tour of the Airbnb HQ from a personal friend, which was kinda unique and cool. Oh, and definitely ride the cable cars in San Fran. It's a really neat experience, and allows you to see a good bit of the city.
Also spent 3 days in Yosemite, which is about the right amount, in my opinion, but you could probably see almost everything in 2 days. We saw most of the major sights in the Valley like Yosemite Falls, Bridalveil Falls, Vernal Falls and the Mist Trail, El Capitan, and Half Dome. Also drove up to Glacier Point to get a cool view of the Valley, plus a closer view of Half Dome. Tunnel View is also pretty cool.
Only spent about a day and a half at Sequoia, but seeing the Giant Sequoias is a great experience. Wouldn't waste your time on the Kings Canyon area if you were planning to go there while you're at Sequoia. It was fine, but didn't care that much for it compared to the other places.
Lake Tahoe was probably my least favorite of the four places, but it's still really nice. Check out Emerald Bay State Park, Inspiration Point, and Pope Beach if you can. Also, the Heavenly Village area of South Lake Tahoe is really cool. All kinds of shops, restaurants, and just a nice overall atmosphere. If you have any other questions about any of those places, just let me know and I can try to provide more detail.
San Francisco was basically at the top of my US Travel list, so I was pretty excited to see it. The Pacific Northwest is right up there though. Definitely trying to do a Portland, Seattle, Vancouver trip within the next couple years. Really wanna see Cannon Beach while we're in Oregon too.