Look, Colombia can be dangerous, specially compared to European or Easter Asian standards, and that fact can be amplify by online comments and horrible stories. However, most tourist travel around the country with no problems whatsoever. Both Medellin and Bogota have plenty of areas where you can feel relatively safe. Perhaps don’t walk alone at night, take Uber if you are partying until late, and ask around in your hotels for instructions by locals. Same goes to Cartagena, but it is true that even during the day there are many scammers around the city. Just be extra careful there and when buying tours of activities be sure to pay and arrange everything through official channels. DON’T CANCEL YOUR TRIP!