Prepare guacamole by placing the avocados in a bowl and mashing them with a fork. Stir in in tomato, onion, serrano pepper, cilantro, lime juice, tequila, salt, and pepper. Mix well.
Heat butter in 2-quart non-stick sauce pan over medium heat. Add flour, stir constantly with wire whisk until mixture becomes pasty. Add butter and milk and stir well until the mixture starts thickening, about 2 to 3 minutes; stirring constantly to prevent flour from lumping. Add cheese and stir until cheese melts, about 1 to 2 minutes; stirring constantly.
Lay out chips on a platter and serve cheese sauce on top and guacamole on the side.