I submitted my AMCAS early July and still haven't received secondaries from UC Irvine and UCLA. I know people who have received them and submitted AMCAS after me. Does this mean that these schools don't really want me?
Yes, you might as well withdraw your applications now.
No, I don't know if it's that big a deal, it's still pretty early in the application cycle. It's possible that they have some sort of system - like take the top 1/3rd based on numbers alone and send them secondaries, then take the next third, and so on (so that way they get them back in waves too). Or maybe it's alphabetical, or maybe by birthday - who knows? I wouldn't start to panic for a few more weeks though (as long as you are certain they have your contact info correct). That's what I'm telling myself since I still have to hear from those schools too!