"The relationship between access to responsive services and treatment completion rates among Latinos points to a serious need for greater geographic proximity to Spanish-language services for this population. Although testing treatment outcomes is not the focus of this paper, it should be noted that studies suggest that linguistic preferences significantly impact the treatment process among Latinos, indirectly contributing to treatment outcomes [5,19,25,26]. In particular, engaging clients in their native language during the intake process increases treatment retention and compliance, which are highly associated with treatment completion and improvements in posttreatment drug use. Similarly, studies have found that limited availability of bilingual treatment services is highly associated with high attrition rates from substance abuse treatment among Latinos when compared to other racial/ethnic groups [27-30].
"Highlighting potential barriers to health care access, such as distance to treatment, is of importance as past studies indicate that treatment completion rates are affected by transportation issues related to distance to outpatient treatment sources [31]. In particular, low-income individuals with significant transportation and communication challenges would be at a considerable disadvantage in terms of addressing their substance abuse issues."

Source

Guerrero, Erick G., et al., "Availability of Substance Abuse Treatment Services in Spanish: A GIS Analysis of Latino Communities in Los Angeles County, California," Substance Abuse Treatment, Prevention, and Policy (2011), 6:21.
http://www.ncbi.nlm.nih.gov/p…
http://www.ncbi.nlm.nih.gov/p…