Even if you have a bunch of young people in one area, it doesn't mean they will mingle with the rest of the city. Stanford for example keeps within it's own bub

Even if you have a bunch of young people in one area, it doesn't mean they will mingle with the rest of the city. Stanford for example keeps within it's own bubble for the most part. There are PhD students who never even go to university street in Palo Alto for example. A Stanford alum I dated for a few months confirmed the same thing. It's only been relatively recently that many tech startups have been moving to SF. It used to be the south bay where many startups lived. You live in SF/Berkley as a single person, you move down to the south bay to raise a family in stable suburbia with 'good schools' vs. the dice roll that is SF. That is the pattern. More tech companies and mostly male tech workers wont solve it. Downtown SJ is already a bit dense as it is.