Pacific Coast Highway/ Yosemite/ Tahoe?

PCH is beautiful and there are a lot of great stops along the way.  I used to practically live at Stinson Beach (north of Frisco) when I lived in the area.  I'd highly recommend going to Yosemite and spending a couple of days there if possible.  With the spring thaw well in effect the waterfalls will be on full display.  I've been there three times and we always did a lot of trail hiking to the various falls.  There are also some great "hidden" swim holes just outside of the park that the locals can point you too that are a blast.  We did some cliff diving at one with my kids and it was our best memory of the trip.

I've driven through Tahoe a couple times and actually got married at South Lake Tahoe but never did any touristy stuff there.  So I'm not much help for that one.

We spent some time hanging out in Sonoma, Yosimite, and SF around Vineman in 2010 (Late July/early August). 

The redwoods are amazing! 

We really liked Yosimite, but keep in mind that unless you stay in the park, it can be quite a drive.  We stayed in Sonora and it's about an hour and a half each way on some winding roads to get into the park.  We didn't pass to many hotels on the way either. 

Fly into SFO and go from there. Northern Ca. is nice everywhere! Tahoe, Yosemite, Mariposa Grove, Marin, San Francisco. I'd head west and hike Yosemite's backcountry. Look into the High Sierra camps and try to get into Vogelsang for a night if at all possible. Tons of great sights and things to do.

Not may places to stay in Yosemite.   We always stay at the Lodge when we go in winter for skiing.  Not luxurious but perfect location.  If you want luxe, the Awahnee Hotel.  There are also the Muir camps, but with the recent hantavirus outbreak and deaths, not sure what the status of those will be. 

Just a point of clarification, the PCH only exists in southern CA, north of SF, it's just CA-1 and US-101.  And from Eureka to Napa, it's kinda boring once you get south of the Redwoods, as it's all inland.  The coast of Oregon is quite nice though

However, I love Yosemite.  For the 6 years I lived in CA, I averaged 3 trips a year there (it was just a 2 hour drive from home).  Two years ago, I did go in May.  It snowed.  When I took this picture, I was halfway up Yosemite Falls, and it started snowing.  Nothing accumulated though.

If you venture out of the valley, you can hike around meadows, and see lots of stuff without crowds.  However, in May, there usually aren't too many crowds anyway, it's still kinda chilly.

Never done too much touristy stuff around Tahoe (also a 2 hour drive from my old place), Nordic skiing in the winter, hiking in the summer.  Can get VERY snowy, or not depending on the winter.  Went for a hike 4th of July weekend, 2011, and had to cut it short due to snow.