Cartagena should be safe as it looks like. But not for us: We were in two, spending some days on holidays. We were robbed in our apartment in "Sol Del Caribe building", located in Laguito, close to Bocagrande.
Area was quite and nice with some peoples on the street were looking for some tourists.
First day one of them approached us at the reception, he was speaking our language and he was friendly.
Second day he disappeared, but another brutal one came in our room during daytime to extort some money from us. Unhappy for that he took us to an ATM for extra cash: what's colombian calls "sequestro rapido" (fast kidnapping).
Bulding should has 24 hours security, but no-one notified us that we were waiting for some visit. When we went out to the ATM main Sol Del Caribe door was open and doorman disappeared, when we came back he was on the desk and door was locked.
It was clear that peoples work in organization, then we were afraid report it to the police and stay there rest of holidays, as well we didn't think someone couldn't do something for us.
If you like to stay in Bocagrande fairly avoid Sol Del Caribe Apartment and its 3 doormans, but strictly choose only apartments with video surveillance where all costumers wear "travel agency bangles" and where you can find security even in the elevator.
And don't forget... beware people on the street even if Bocagrande looks like the safest place in the world.
With Cartagena being on the coast my first impression was the fish would be plentiful and great to eat. However before we left I read an article by the U.S. Center for Disease Control on eating fish in Cartagena. Because of extremely high mercury levels it urged caution. It also suggested to never eat raw or undercooked fish, including cerviche. Some types of fish may contain poisonous biotoxins even when cooked. Fish that may contain toxins include red snapper, grouper, amberjack, and sea bass. Hey I know this sounds like no fun but believe me it is not nice to get sick or food poisoning in South America.
If you pay for something in cash using the local Columbian peso I have noticed that many times merchants, if they expect you are a tourist, will hand you your change without counting it out. Since several of the pieces of currency you will be using is in high denominations it is easy to get confused. Be sure when someone gives you change, regardless of it is in a small shop or top notch restaurant, that you count the change in their presence. This will assure that you receive the right change back for your purchase. A simple guide book will help you with the names of each of the bills and coins.
You will see numerous street vendors and ladies walking around selling large varieties of fruit. More times than not much of the fruit that is sold in this way is either old, moldy or full of bugs. As tempting as it may look better to go to a supermarket where the quality will be more certain.