Sutphin Boulevard/Archer Avenue/JFK Airport subway station machines are very crowded. There are two machines on the opposite side Archer Ave may have a shorter line, all depending on the time of day. As Yoshi says a metorcard can have both unlimited time and cash on it. Where cash is used not the time like Airtrain/PATH/Express bus the card will debit that balance just can;t use the cash balance when the unlimited is being used like swiping a 2nd person into the subway.

You may want to check a Hudson News outlet in the airport they sometimes have metrocards, of course the prepaid balance of airtrain and one subway ride won't help you but doen't hurt to see if they have a weekly then just add the $5 for airtrain at airtrain stop.

Of course you could take Airtrain to Howard Beach A train, no crowds there!!