Remove casing from chorizo. Heat skillet over medium-high heat. Crumble chorizo into skillet; cook, stirring frequently and using a spoon to break up lumps, until sausage is well-browned, about 5 minutes. Remove sausage to paper towels to drain.
In a large microwave-safe bowl, combine Mexican cheese, cream cheese and milk. Microwave at Medium (50% power) stirring every minute until melted and hot, 6 to 8 minutes. Alternatively, you can prepare in the top of a double boiler over simmering water, stirring constantly, but melting time may differ.
Stir in chorizo, tomato, green onion and jalapeno. Place in fondue pot or slow cooker to keep warm. Serve with garlic tortilla chips.