Solid waste management (SWM) is a major global challenge for environmental sustainability and public health. This study analyzed SWM perceptions and practices before and during the COVID-19 pandemic in Playa Boca Chica, Tecpan de Galeana, Guerrero, Mexico, using a descriptive and quantitative approach. Data was collected from 60 households between September and October 2022 and analyzed using SPSS statistical software version 26; reliability was confirmed with Cronbach’s Alpha; and the generation-associated greenhouse gas (GHG) emissions were estimated using the SWM-GHG climate calculator. This study explored socio-environmental dynamics in informal coastal settlements through a case study in the Global South. The results showed that waste generation remained stable during the pandemic (3.25 kg/day; p = 0.116), suggesting a pattern of behavioral rigidity in which entrenched waste management practices persisted despite the global health crisis, likely due to the absence of structural environmental interventions and policy-driven behavioral incentives. The climate calculator estimated GHG emissions of 92 and 99 tons of CO₂-eq/year before and during the pandemic, respectively. Residents highlighted the need for improved infrastructure, recycling, and composting, while 97% emphasized environmental education and waste separation. The absence of a local waste management policy contributes to persistent emissions, underscoring the need for integrated and sustainable SWM strategies.