Hi there...i just recently contacted immigration because I am planning to go to Mexico by January and ask them what is the best thing to do when i want to leave Canada while my PR is on process and their answer is there is no guarantee that you can go back unless you will meet all the requirements even you have open work permit on hand. The best thing for you to do is phone immigration and tell them your plan and your situation that is the best thing to do. This is their phone number 1-888-242-2100.