hi
Colombian people are very nice with the foreigners. At least thats my experience.
the only place that i been told to be in the wrong place was in Berrugas, nice place but... not safe at night.
if you want to go up to sierra nevada de santa marta you need to take a guide. it is not safe otherwise.
of course there're areas in the cities where you feel it is not a good place to stop but provably paris or london are more dangerous than Colombia in general.