It depends what period of history you're talking about. The island of Crete was settled by Greeks during the Mycenean period. Evidence suggests that they brought their language with them.
However, I assume you mean the earlier civilization that created the Minoan palaces. The short answer: we don't know what language they spoke.
Have you tried doing a google search on this? The keywords "Linear A" and "Linear B" should help you get started.
IPHIGENIE: Kann uns zum Vaterland die Fremde werden?
ARKAS: Und dir ist fremd das Vaterland geworden.
IPHIGENIE: Das ist's, warum mein blutend Herz nicht heilt.
(Goethe, Iphigenie auf Tauris)