My group has been going to Cancun for 18 years and some years back we enjoyed painting pottery with Mercedes at the Calinda Beach (as it was called back then). We would love a day at the beach with painting but it seems it is mostly offered at all inclusive resorts. We stay at the Flamingo Hotel but will travel to where painting may be offered.
The Royals have the painting and you can pay them direct. I would just go in like you own the place and at the Royal Sands the painting is done out by the pool. Just go and find a piece you want to do and paint it. VCI has it and its over by where the towels and tennis courts are.