The most convenient way is to go to Guayaquil Ecuador.

When you arrive the Guayaquil airport you can easily walk to the Bus Terminal or take a taxi (the recommended option for safety, not cost more than $ 3).

Alternatively you can take a taxi or combi to Montanita (about $ 35 minimum).

From the Bus Terminal of Guayaquil

There are three schedules to take the direct bus to Montanita: 8 am, 13 pm 17 pm
But all day you can take a bus to Santa Elena / Libertad city.

You can take a bus from Guayaquil these cities and then from Santa Elena a bus to Montanita

These buses depart from the same place that the direct bus (bus terminal in Guayaquil, 500 m from the airport)