You must defend the Taco Stand from the zombies, and also do not let zombies get the tacos to Zomboss's UFO three times, or else you will lose. The tacos takes 5 seconds to reset to its base.
For Team Zombies[]
You must get the taco from the Taco Stand, you cannot use any abilities while having the taco. You have to get a taco to Zomboss's UFO three times to win. Also, do not forget only one zombie can take a taco each time, so to get another taco you will have to wait for the zombie with the taco to be vanquished or the zombie to take it to the UFO. As Scientist, Warp just before picking up the taco. As All-Star, Sprint Tackle simply into the taco stand.
This is the only game mode where spawnable zombies can be spawned in a normal map that isn't a Gardens & Graveyards map.
This is not true in Garden Warfare 2 since in Gnome Bomb potted plants and bots can be built/planted.
In the September 2018 patch notes, the team discussed about game modes, claiming that they will keep the players "well-fed with fun", hinting at the return of Taco Bandits.
This was officially confirmed when the December 2018 update was released featuring a limited time game mode called "Capture the Taco" which was similar to Taco Bandits, but allowed both plants and zombies to take part in capturing the other side's tacos.