Preheat oven to 375 degrees F.
In a medium size bowl combine the eggs, milk, garlic, cumin, and salt and pepper, and lightly beat. Dip the bread slices in the egg mixture covering both sides. In a baking dish lightly coated with olive oil, place a layer of bread slices on the bottom. Arrange a layer of avocado slices in a fan design on top of the bread. Cover with a layer of Monterey Jack. Place another layer of the dipped bread slices over the cheese and avocados. Bake in the oven for 15 minutes, or until bread is nicely browned.
To make the tomato jam, saute the tomatoes and sugar in a pan until liquid reduces and becomes thick.
In a medium size pot, reduce the vinegar until slightly thickened.
To serve, remove the avocado cristo from baking dish and cut into wedges. Arrange wedges on each plate with the plum tomato jam and a drizzle of the balsamic reduction. Garnish plate with lime juice, chopped cilantro, and a slice of avocado.