Do your pivots quietly and cheaply in Detroit or Des Moines and once you have an executable and repeatable business model, then and only then consider the Valley.
They Silicon Valley's days aren't over, but with the rapid growth of hacker spaces, incubators, angel groups, and other SV "services" in other areas, the need to be in SV is diminishing.
Stay where you're successful and help build your own local SV type services.
But there's no sense in leaving once reaching success. Reinvest it in the community that helps bring you up. Build something bigger. Repeat.