In the short story "No Speak English" by Sandra Cisneros, Mamacita does not leave the apartment primarily due to her feelings of isolation, cultural disconnection, and fear of the outside world. One piece of evidence that supports this is her reaction to her surroundings; she is overwhelmed by the differences between her old life and her new environment. She often looks out the window longingly but rarely steps outside, indicating her reluctance to engage with the unfamiliar world outside.
Additionally, her attachment to traditional values and her inability to speak English further contribute to her sense of isolation, making her feel more comfortable within the confines of her apartment where she can reminisce about her past and maintain her cultural identity.
These aspects highlight how her fear and cultural ties prevent her from fully integrating into her new environment, ultimately leading her to remain inside the apartment.