List Source - Language and Ethnicity Query

[Cal Ewing]

Hey BP, 

I am toying with the idea of sending my direct mail pieces written in Spanish to addresses that are predominantly Spanish speaking because my farm area has a lot of Hispanic people living there. 

I feel that if I were the homeowner and I was most comfortable communicating in Spanish and I got a piece of mail in my native language and one in English, I might choose to call on the Spanish letter or postcard.

I am wondering if anyone has used the "Language" or "Ethnicity" query on list source and how reliable the results are?