There are two Trader Joe’s grocery stores close to MARTA, the Midtown or Buckhead locations:
Exit at the Midtown Station on the red/gold rail line, take the Peachtree Place exit out of the station and turn left. Walk about four blocks. You can also board bus 109 or bus 36 at the station — it is free to ride the bus when transferring from a train.
Exit at the Buckhead Station on the red rail line and take the Peachtree Road exit out of the station. Go up the first set of stairs to street level. Wait there for bus 110, or turn right and walk about 15 minutes.