Volaris is putting Mexico City on sale from Los Angeles for travel between January and May (with limited availability in April), with flights starting at just $195, direct round-trip, after taxes.
These flights are direct and time in at a at least one layover, and time in at around 7-8 hours each way.
Mexico City is one of my favorite cities in the world, and you can make a long weekend of it with little effort from the West Coast.
To find this deal, use Google Flights and search for flights between LAX and MEX.