Already in the works for a year, the project's future is in the hands of the people who would be most affected by it, López Obrador said Friday.
But critics question whether communities in the region have all the information they need to make a decision., and say it poses possible environmental risks and could drive land speculation.
The Mayan Train would run 950 miles (1,525 kilometers) around the peninsula connecting the white-sand beaches of the Mayan Riviera resorts with archaeological sites in the interior and the colonial city of Merida.
The public vote Sunday will be combined with two days of regional meetings with indigenous groups. Mexican law and international treaties require consultation with those communities.
But López Obrador described the consultation as way to head off his opponents' attempts to delay or stop the project. The government is rushing to build it before his six-year term ends in 2024.
López Obrador earlier used a public referendum to scrap a partially built new airport for the capital by his predecessor.
“We don't want the conservatives to have a pretext or excuses to stop a project that is going to take four years to build and an investment of $6.2 billion to $7.8 billion,” he said. He planned to visit the region this weekend.
But doubts exist about how much information the region's residents have to make an informed decision. The government's tourism arm has been very active spreading its promotional message, but others say objective information has been hard to come by.
Sergio Prieto Díaz, chair of the Migration and Trans-border Processes group at the College of the Southern Border, said he was waiting to see how the consultation played out to know if it is real or just a simulation to give the government's plan legitimacy.
He said it already has divided communities. “There are people in favor and opposed. The problem is that neither one nor the other has objective, complete or reliable information and this sets off speculation and conflict with unforeseeable consequences.”