I posted on another thread yesterday that I had been to Cartegena, I went on Princess cruises and I found the port very nice.
Now we were all on escourted shore trips and controlled a bit, I remeber being taken up the mountain and we had a great view of our ship, then around the beautiful old town and ended up in jewerly shops of course specailist in Emeralds.
Now at parts the locals did try and come up to us, they are poor and want anything they can from you, people did swam around a bit at the port entrance but in the stops it was very controled and safe.
The Jewerly shops were good value we had our purchases valued in London afterwards in Hatton Garden our center for this and they were a good price, but care on stones with a slight flaw. Size and weight good but there could be slight imperfections.
The place was hot but ok with that and we were taken also to a beach and treated to drinks etc. There were and maybe more development with lots of new high class hotels.
On organised trips you will be ok with a local tour guide, I would not recommend doing it youself here there are security risks, but also not to worry its an enjoyable stop close to panama and will break up the long sea days from 2005