Hola Isabel,
Your recipe for Arroz Con Leche sounds delicious, but it is much more refined than what typically appears in our part of Mexico. Like you said, instead of risotto rice here "arroz super extra grano largo"/long-grained rice is typically used and instead of double and heavy cream the dairy of choice is condensed sweet milk (the sweet condensed milk also being used in such postres as pastel de tres leches, sweetened fresh corn bread and a variety of gelatins).