I am nearly 40 and most of the developers I have worked with in the past 10+ years have always been older than me (aside from college new hires). They have also been 20-40% female. I have spent this time working in the Westlake, Irving, Plano technology corridor of north DFW.
I would like to hear what kind of demographics people encounter by geographic location. I always hear about age and sex bias online, but I simply don't see it in my area.
Established companies with good work-life balance, solid benefits, and internal advancement opportunities are much closer to your experience.
1 - Edit because I've been hammered for saying this before. Many studies have shown significantly increased financial, business, and physical risk taking in men. That's the type I'm referring to.
From my experiences a lot of SV's ageism is not really that they won't hire older workers on principle, it is just that most of their worker are young due to local conditions and like attracts like. By 'local conditions' I mostly mean cost of living, everyone I know who has lived in SV moved away when they got older and wanted to start a family.