I will NOT be connecting 6 accelerometers to one arduino. Each sensor has it's own board.
That wasn't clear from your first post. So, you plan to equip a person with 6 Arduinos, each with an XBee shield and XBee and accelerometer. That will get expensive.
From the documentation i found that one receiver can receive from more than one transmitter.
Yes, as long as the amount of data is manageable and there is some way to identify which accelerometer/Arduino/XBee the data is from.