Costa Maya was our favorite port! We took a cab to Mahahual (10 min?) and spent the day playing on the beach, getting massages ($20/40 min) and THE best margaritas I've ever had! My (then 14yr old) LOVED mahahual---VERY authentic mexican culture. We were in Coz the next day. We walked around town and did a little shopping. It was a fun "girls" day. They may be close geographically but worlds apart, as for tourism.
I'm anxious to return to CM, when they re-open to cruise's...I only hope it will be as beautiful as before DEAN. Unfortunately, there is no way to know.
Please consider giving it a try. The locals were totally dependent on tourism...with the hurricane closing the pier, they will need our support.