The question was:
I am a US Citizen and a citizen of Ireland and hold passports of both countries. But, my permanent and only residence is in Mexico and I will be flying from Mexico city to Madrid to start my camino. I plan to be in Spain for a maximum of 60 days at which point I will return to Mexico.
Do I need any visa? Which passport should I travel with?
Read the good conversation related to Visa requirement for traveling to Spain and the Camino de Santiago here.