I called Mexicana Airlines. Their cancellation policy is fluctuating as they get info from the resorts as to their reopening, as well as other factors. Their normal cancellation or change fee is $100. However, this doesn't apply to flights to CZM through Oct. 30 (no cancellation fees). As of this moment, flights in November and December are still subject to that $100 cancellation/change fee, but that may change. She said to check back in a "couple of days" because they may have updated their policy by then. She said they understand the situation and are trying to help people. (Imagine that!)
Also, I called the 800 number of the Grand Cozumel/Occidental since they were supposed to have info about their reopening. The operator said that they were going to reopen on December 20th. I asked her when they were going to post that information and she said "later," so I'm personally a little skeptical of that date. (I wonder why they'd reopen the resort on a Tuesday?) Anyone hear anything different?