IDK about elsewhere but East of the Rockies, at least, yes, they're basically used interchangeably in many contexts and nobody cares that a "Silicon Valley" story may in fact be about a company based a few miles from actual Silicon Valley. Sorta like how nobody outside New York cares about the distinction between the boroughs except maybe Manhattan, so including or excluding that information, versus just calling it all "New York", makes no difference to them (/us). In fact I bet a lot of folks think "Manhattan" and "New York (City)" are perfect synonyms, and really, it doesn't much matter that they do.
That's a common misapprehension among people that don't live there.
For anyone in the Bay Area, Silicon Valley is some ways south of San Francisco.
That said, a lot of startups are in SF, because Silicon Valley is too expensive (though SF itself is catching up because of the second dot com boom/bubble), so it's not surprising that outsiders lump the two of them together as a hub of Bay Area tech activity (which they are.. but they're just two distinct geographical areas).
