DELE is a Spanish language proficiency level certification offered by Spain. Is there any equivalent certification offered by Mexico? For example, in English there's the IELTS for British English and TOEFL for American English. Similarly DELE is for Spain's Spanish; what is the equivalent for Mexican Spanish?
DELE is offered by Instituto Cervantes which is the founder of SICELE together with many universities from America.
So I am quite sure that DELE is not restricted to just Spaniards; many Mexican universities are on the list.
By the way in Nueva Delhi, Pune, Ahmedabad, Kolkata and Chennai there are schools that offer DELE exams.
Offtopic: I see that you tend to ask many questions related to the differences between the Spanish spoken in Mexico and the Spanish spoken in other countries. It is true that a teacher should know these differences, but as a student I recommend you learn just one, and when you become good at it, you should have no problems figuring out meanings in other countries. In my opinion, Spanish is more elaborated grammatically and orthographically than English, once this base has been learned the rest is phonetic. Imagine if I had to learn all English accents.