Mexican artists colony around Cancun/Playa del Carmen/Tulum?
 

We want to buy some Mexican art and we don't want to travel to, say, Merida. Don't mind traveling a few hours.

We're looking for a painting of some kind.

Any suggestions appreciated.

You might try taking the ferry from Cancun to Isla Mujeres. There are lots of great handicrafts - I don't remember paintings specifically, but I wasn't in the market and it's been a few years ago. It's a nice day trip, in any case.

By the way, you're missing out if you skip Merida. :D