You misread the original question "how 11,000 poor as dirt Haitians got from Haiti to the Mexican border?"
You can't get from HAITI (AN ISLAND) to anywhere in North, Central, or South American by any form of ground transportation (walking, car, bus, truck, train, donkey, etc....) because it is an ISLAND with no bridges connecting it to any other land mass. Therefore, you must take a BOAT or an AIRPLANE.