Honestly depending on what your planning quanity wise to bring back I would consider packaging them flatly like you spoke about and put them in your checked luggage. Injectables I would bother mailing. Either way its a risk. I recently flew to cancun and carried shit through customs in my carry-on without a hitch.
500 dbol i was still sweatin it but somethin to think about. I figured out the airfare and expense and If I flew to Mexico City from my city bout gear sent it back stayed for two days I could match and almost beat my sources prices.....But its risky and Im lazy