I have been around the world on this little post divorce adventure... In Colombia I have been to Medellin, Cartagena and Barranquilla. There is just no comparison. Barranquilla first off just sucks. It's an awful, decentralized, ugly, industrial, dirty, dangerous city. Medellin certainly has hot women, but the city itself while not dangerous is dumpy, ugly, hard to navigate, no where to walk, etc. I found a few nice casas but they are scattered around and difficult to deal with. Everything has to be by taxi.
Cartagena is HIGHLY RECOMMENDED. I did best flying with COPA... Avianca is the one where the pilot ran out of gas and crashed on Long Island, no thanks. Copa flies direct for me from LA to Panama and then to Cartagena. There are many flights from other US cities to Panama for the connection. Here is a city which has a HILTON hotel and also many cheaper ones (I stayed at the Dann $105/night phone 0115756650000 and the Cartagena Plaza $77/night phone 0115756654000). Nice places to walk, things to see, an historic old city, beaches, islands, ETC. Great food, very smoking hot chicks both of the girlfriend and paying variety. I posted some photos, check them out and don't hesitate to visit. The "dangerous" part of Colombia is the jungle area in the southern part of the country. Here there are police, tourist police, military, etc., they don't want anything weird happening to a foreign tourist.