I have heard someone say that a P.O. Box was accepted in his case. Otherwise, I have heard that you could arrange a street address with UPS and have them forward your mail to your address in home country. However, immigration would prefer that you use your real address in Canada to minimize the possibility of your PR card getting lost.
If you don't have an address, it is not a problem. Just tell them when you land that you are only staying for 2 weeks and to please hold your card. When you are ready to return to Canada to stay, if you are visa exempt to Canada, you can go with your passport and landing papers and if you need a visa, you apply for a PR travel document at the Canadian embassy where you live.
Once you are in Canada to stay and have an address, if it is 6 months or less since you landed, you can contact CIC, tell them to send your PR card and they will. If it is more, like PMM said, fill out an application for a card, pay $50, get new photos and send it in but in that case, they will not mail it, they will make you pick it up at their local office and it will take a bit longer.