It is the primary setting for Season 1 of the series.
Carol Pilbasian moves next store to Phil in "The Elephant in the Room" inside Bonita Estates. As more survivors come to Tucson, such as Melissa, Todd, Erica, Gail, and Phil , they all move into the mansions in the cul-de-sac.
When Phil/Tandy threatens to kill Phil (II) in "Screw the Moon" , Phil decides to kick Tandy out of Tucson. Tandy keeps himself locked in his mansion for three days. When he comes out, Phil kidnaps him and brings him to the desert to die. Carol decides to go after Tandy and be with him. The two leave behind Tucson and head on a road trip of there own.
When Phil/Tandy and Carol are separated from each other in "Is There Anybody Out There?", Phil believes that she had gone back to Tucson. Phil returns to Tucson to find the cul-de-sac deserted and his house torched. When Phil and Carol finally find each other in "The Boo", they decide to move into Carol's old house. While there, Phil finds a note saying that the survivors have gone to Malibu. The two decide to go to Malibu together in order to see the others.
After crash landing on Earth, Phil's astronaut brother, Mike Miller, eventually makes his way to Earth and Tucson. After landing in the ocean, and meeting and ditching paranoid seaman, Pat Brown, he eventually travels to Tucson. As explained in "Skidmark", Mike traveled to Tucson and visited Tandy's old apartment, and upon finding it empty, he presumed Tandy would have moved to Bonita Estates. Immediately arriving there, he found Melissa's note to Carol saying they went to Malibu, leading him to go there and successfully meeting up with the group.