Celaya is a remarkable city with lots to offer, however, the safety concerns cannot be dismissed. As a solo female traveler, one should be cautious especially during the night and in less crowded areas. More touristy areas and during the day tend to be safer. It's advised to always be vigilant, avoid displaying wealth and keep regular checks with someone back home about your whereabouts. As in any city, take care when using public transport and always use a trusted taxi company or Uber. Remember, language could also be a barrier, having knowledge of basic Spanish can be of help. Don't forget to use your common sense as you would do in any other place in the world.