I live in the bay area, moved from new england (boston), let me give you the skinny on the three most important things about the area.
One, rent. Rent is expensive. Slightly more expensive than boston, and boston ain't cheap. On the other hand, houses are 2-3x as expensive. With that said, you can find good places if you look hard. I would figure: $800-1000 for a room, $1500 for a studio, $2000 for a 1-bed, in SF itself. However if you live in eg Oakland, your rent drops considerably to approximately your estimates. The shittier the neighborhood, the cheaper the rent, but that math gets wonky when you start worrying about your car being stolen and your place burglarized. The worrying is a spectrum depending on the person - I'll gladly live in places that some other people (especially single women, or families with kids) won't touch with a 1-mile pole. SF is similar except SF has much less middle ground - $1000/month gets you a 1-bed in the tenderloin, which even I'd rather not live in. Expect rent to be your single biggest expense, but if you're smart, it'll be 20-30% of your post-tax pay. Don't do the whole 33% of pre-tax pay thing, it ain't worth it. Apart from rent, cost of living is very similar to what I've seen around the country wherever I've lived.
Two, career opportunities. The valley is huge, and at the same time, smaller than you'd think. What that means is that there are tens of thousands of opportunities that would fit your career and interests (unless you're doing something incredibly specific), yet at the same time, your "kevin bacon" number to the guy interviewing you might be smaller than you'd imagine, especially after you live here a while. It is standard that you get a new job and immediately know a couple people from previous jobs and from social friend-of-friend type things. As your career progresses, hiring gets very informal - manager needs to hire, asks around, your name pops up, you chat over coffee about what problems need to be solved, you indicate interest, depending on the company a real interview is organized, you have a job. Often it's even more informal - you just pop in to a startup, chat a bit, start next week. Oh, yeah, have I mentioned startups? The culture means that even non-startups give you equity (RSUs), and startups give you lots (whether it's actually worth the electrons used to display it on the screen is a different matter - a lot of equity is worth about $50 after it's all said and done.) But there's always the chance of a massive reward that keeps people churning out new ideas (even if many of them are stupid.)
Three, weather. Let me make no exaggeration here. I spent 95% of my weekends out and about and/or entertaining friends at my place since I moved here. That includes rainy october and november weekends. You just have no idea until you're here just how goddamn much there is to do if you want it. If you like going out, there's a mind-boggling number of restaurants, bars, and clubs. I'm not a huge fan; I like hiking. Do you know how many places there are to hike here? I can go to a different place every weekend for three years and never go to the same place twice. I can go to a different trail every weekend for thirty years and never go to the same trail twice. By the time I'm done the trails will have changed. Of course, that's supported by beaches, windy mountain roads for biking / motorcycling / driving, various turnouts on every goddamn road to just stare out at the lovely landscape, Route 1 which combines the above... mountains, valleys, wildlife, sun and shade, water and heat, whatever you damn well please. Oh, have I mentioned the national parks? There are a bunch within driving distance. National forests, too. And of course state parks and forests and wildlife preserves. Not a fan of the great outdoors? Let's add museums, parades, cultural and science centers, landmarks, aquariums and zoos, and just places to walk and see. Like driving? We have race tracks. Scuba diving? There's that. Seriously, I don't care what you like, unless your main hobby is "netflix," you'll never be bored here.