They don't have to read you your rights at any time. If they never read your rights, they can't use anything you say against you. They don't have to read you the miranda at all if they don't want to. I got popped this past summer with 2 other dudes-- nobody got their rights read to them. Our charges were dropped only because of age. I assume once you start spilling shit and dropping names (or refuse to say anything at all) they will read you your rights before anything else happens.
Check in with ACLU if you have any questions; that's what they're there for.