You can dive the entire east coast of the yucatan. My son and I took a road trip last year from cancun to xcalak. We dove in akumal, tulum, mahaual, and spent three days in xcalak with xtc divers. Fun trip, we liked the road trip aspect. Didn't book in advance, as we had no set plan. Although it was a holiday week we were able to find accomodations each night, some better than others. I can recommend costa de cocos in xcalak. This may not work for you, but if you are a flexible traveler and like to explore the road less traveled then you might enjoy a trip like this. Good luck happy divin.
Mahahaul = We are staying 2 weeks in Cancun in October. We have dove that area quite a bit and wanted to go South. We are looking at Maya Palms diving resort in Mahahaul. How was the diving there when you went with your son? We have read the barrier reef is extremely close to shore as well as more virgin than anything near Cancun/Cozumel. Any input would be appreciated.