Explanation: If the context is all about ethnicity, there should be no need to qualify the term in any specific way. It will be understood not as a designation of citizenship or "nationality," but as a designation of ethnicity.
If the context is not all about ethnicity and thus may be ambiguous, I would then quality the term as
Thanks to both of you. This was a difficult decision which I took based on popular usage. In his argument, sami mentioned هسباني, which reminded me that almost every Arabic speaker I know calls hispanics إسباني without regard to Spanish or non-Spanish origin. Because the forms I am translating will be filled by lay people, I opted for this choice. 4 KudoZ points were awarded for this answer
Sami. Thank you for your suggestion. What prevents the argument that you applied to أسباني from applying equally to لاتيني? It seems that Hispanics are only Latinos because they speak spanish, which is a Latin language.
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4 mins confidence: peer agreement (net): +10
أسباني
Explanation: If the context is all about ethnicity, there should be no need to qualify the term in any specific way. It will be understood not as a designation of citizenship or "nationality," but as a designation of ethnicity.
If the context is not all about ethnicity and thus may be ambiguous, I would then quality the term as
أسباني الأصل
أسباني المنشأ
or even
أسباني الأثنية
and so on.
Fuad Yahya United States Works in field Native speaker of: Arabic, English PRO pts in category: 185
Grading comment
Thanks to both of you. This was a difficult decision which I took based on popular usage. In his argument, sami mentioned هسباني, which reminded me that almost every Arabic speaker I know calls hispanics إسباني without regard to Spanish or non-Spanish origin. Because the forms I am translating will be filled by lay people, I opted for this choice.
The translation workplace 
peer agreement (net): +10