Yes, just make sure that you log into one account and Authorize that computer for that account and then log into the 2nd account and authorize the computer for that account as well. I do this because my wife and I both have iTunes accounts and we share our purchases. Once you do this, you should be able to sync with anything from those 2 accounts without being logged in.
I confirm this is possible, even with iTunes accounts from different countries. I have UK and Swiss accounts synced to my device currently. Had to do this to get the Google app which still hasn't been released in the Swiss store.