Still some dates available at 344$CAD May-June-Oct-Nov-Jan-Feb , coupon is still working 34$ off so 308$CAD. With 1 day stop over in Panama City, good opportunity to visit that city.
Use coupon AFFBFAN to get a 32$ rebate on Copa website
Ex: Jan 25 to Feb 8 with a 1 day Panama city stop
Other dates: May 3 to 12 / June 8 to 22 / Oct 18 to 24 / Nov 2 to 10 / Feb 1 to 9 /
Copa is a partner of Star Alliance, ticket code fare is E so you’ll get 100% of Aeroplan miles flown with them, so around 5740 Aeroplan miles for this trip.
Seach dates here on Google flights https://www.google.ca/flights/#search;f=YUL;t=SJO;d=2017-01-25;r=2017-02-08;sel=YULPTY0CM423-PTYSJO0CM116,SJOPTY0CM115-PTYYUL1CM422;a=CM
If you have trouble to book with Copa with your credit card, switch to USD$ instead of CAD$, happens to me when I did book this deal. I called them about it and they want me to book on the phone with them but there is a fee of 30$ so I went back on Copa website, switch to USD$ and went thru.