I spent a few days by myself in Cartagena on the coast of Colombia. Beautiful place but I think my expectations were too high going into it. I had heard such great things that I was preparing for paradise. Instead I got weather way too hot and tropical for my SF-fog-drenched self. Plus I'm not too into old colonial buildings — I've seen it a million times in Europe.
The beaches aren't bad — better than I had been told. The people are friendly. Coastal food a bit different than in Bogota. Very walkable.