Not all startups are created equally, so it definitely varies, from the people who have worked at startups that I know.
Typically a startup only hires from its region - airfare is an unnecessary expense, really. So for a "true" startup, we're talking Stanford and UC Berkeley, basically, for the Silicon Valley.
More "established" startups that are already successful or already widely recognized might travel to East Coast schools and SoCal schools.
I know several people who go to school on the East Coast (Ivies and LACs and Duke), but since they live in Silicon Valley, they often work over the summer at one of those "established" startups (engineering and business).
I also know a rising freshman who is attending an Ivy next year for CS, and he's the first employee of a startup, but again, he lives in the Silicon Valley.
However, Boston is probably second to the Silicon Valley in terms of startup/VC density, with NYC third, so if you got to school on the East Coast, there are tons of startups in those two cities.