No, you are not eligible for PRTD until you get the eCOPR. as the name PRTD suggest permanent resident travel document, you are not a permanent resident until you get your eCOPR hence you are ineligible. You can come back to Canada on your current travel documents e.g. visitor /work/study visa but the moment you get your eCOPR, all of your previous temporary resident documents are invalid. Then you need either a PR card or a PRTD to enter into Canada.