Are you permanently disqualified from joining the Army if you fail MEPS?

If you don't meet the minumum standards for enlistment then you won't be permanently disqualified from enlistment, you'll be temporarily disqualified until you can meet the standards. The only thing you can do at MEPS that would permanently disqualify you (outside of having a criminal charge or medical condition the permanently disqualifies you already) is come up positive on the drug test.