I hope OP listens to this. Spend 80% of your time in SF/Oakland/Berkeley and 20% at most in SV. The former is one of the most interesting, beautiful metropolitan areas in the world.; The later is a fairly mundane suburb.

When I'm visiting the Bay Area I like to go to coworking spaces as well.

What do you do at co-working spaces (aside from work?) Is it to meet people or what exactly? (I've been been)

CHM is in Mountain View. Come on Wednesday to watch the live demo of an IBM 1401 system or see the RAMAC (first commercial hard disk) running.

http://www.computerhistory.org/visit/

The Computer History Museum is in Mountain View, not in San Jose. If you go to Stanford you might as well go there too.

I realized that after I wrote it. I'm conflating my technology-related museums.

Would a week or a week and a half be long enough to visit and see a good amount of stuff?

Certainly not everything--especially if you're talking the whole region from Pt. Reyes through Sonoma/Napa to San Francisco, the South Bay, and Santa Cruz/Santa Cruz mountains/Monterey. But 1-2 weeks is enough to give you a nice flavor of the area. I'd probably pick SF and maybe a couple select things to see/do in the Valley and then spend some time either north or south from there.

I just have a lot of vacation days to burn still and I've ALWAYS wanted to visit SF (other than the airport).

SF is one of my favorite cities (to visit :-)). And there's tons of other great stuff to do within driving distance from 1-2 hours on up. (You can reach the Sierras but I probably wouldn't recommend that for a first time visit of limited duration.) IMO, great choice for a vacation of just about any length.

Vegas vs SF? Which would you choose?

Oh good lord. Not even close. Maybe Las Vegas is a bucket list sort of thing to do once for a few days. (I, sadly, have spent a great deal more time in Vegas than that.) There are very interesting places within a few hour radius of Vegas if the weather isn't too hot--Death Valley, Zion, Red Rock Canyon, Hoover Dam, Grand Canyon. But I wouldn't spend money or time to go to Vegas itself voluntarily.

I went for a few days to Vegas for work (first time going) and enjoyed it for the time I was there.

Other than that I've been trying to wait until a band I really want to see plays at Red Rock until I go there.

SF.