It's clear from your other thread that you are flying out on American, but that info would have been relevant here as well. If you had been flying Delta you could have checked in at Domestic, even for an International flight.
For future reference, it's best if you go ahead and include ALL the info about your travel plans in your initial posting. We might give different advice for different situations (domestic vs inyernational, which airline, etc) and you'll get the best overall advice if you provide the necessary detail up front.
Thanks everyone for all your help!!