pitot tube down

A portion of thread from different news grope:

loss of a 757 a few years ago in which clogged pitot tubes
caused bad overspeed warnings; the Turkish crew pulled
back the power and stalled and crashed. It was later determined
that the A/C had sat for a month and insects had gotten into
uncovered pitot tubes.

With aircraft equipped with GPS that shows your true speed, can you fly by
it when pitot tube is down?

Emilio.