There may be some specialty carriers that will insure you in the United States with an international or foreign license, but most insurance companies require you obtain a driver's license in the state you reside (in your case MA) before purchasing insurance or within 30 days after obtaining coverage.

According to the Massachusetts Registry of Motor Vehicles (RMV) if you are from a country listed in the 1949 Road Acts Convention, you must have a sponsor and you must present your valid driver's license from that country and if needed, an English translation of the license in order to convert a foreign license to a Massachusetts license. Ecuador is listed on the aforementioned 1929 Road Acts Convention.

An International Driving Permit (IDP) cannot be converted to a Massachusetts Driver's License. An International Driving Permit does not confer any driving privileges but is a translation into ten major languages of the relevant information contained on the driver's home country license.

The Massachusetts driver's manual gives more information on the Road Acts convention. Here it states that a foreign visitor from one of the countries or territories listed here may legally drive on the roads of the Commonwealth on his or her own country’s license (limited to a licensed driver who is at least 18 years old and limited to a vehicle of the type covered by the license) for up to one year from the date of arrival. So if you are going to stay over a year in the United States you will need to obtain a State license in order to drive legally.

To find out if you can buy and register a car in Boston, MA with the Ecuadorian license, check with the Massachusetts RMV. You may find out that you will need to get the MA license before acquiring a car, registering it or insuring it