Guanajuato Â· Population. Question: What is the population of Guanajuato? Answer: Guanajuato, Mexico (Administrative unit: Guanajuato) - last known population is â 70 800 (year 2014). This was 0.056% of total Mexico population. If population growth rate would be same as in period 2010-2014 (-0.5%/year), Guanajuato population in 2017 would be: 69 741*.