No need to rent a car in Cartagena! (There are complicated rules about driving cars around the center area anyway which would make having a car undesirable.) It’s easy to walk around the Old City & other means of transportation are available.
Cartagena’s ubiquitous yellow public taxis are easily flagged on the street & in general are safe. Fares are set by zone and by law, each cab is to have a copy of the zone fare card available. As of March 2017, the minimum fare is COP$6,400 and there is a 500 peso night surcharge from 9 pm to 5 am.
*From the airport to these Old City & Cabrero apartments: $10,400.
*Between the Old City & Cabrero, Bocagrande, San Felipe Castle, Manga: $6,400
Additional 500 peso night charge between 9 pm and 5 am.
In practice, fares may be rounded up to the next highest thousand. Tipping is not common or obligatory but always welcomed.
Popular apps for calling taxis in Colombia include:
Uber (although note that Uber has dubious legality in Colombia; if you use Uber you will likely be asked to sit in the front seat to avoid suspicion)
Integrated public transport system “TransCaribe” started in late 2015 with comfortable seating and air conditioning! The main lines run on a dedicated bus lane from the tourist dock to the southern areas of the city along Avenida Pedro de Heredia. You need to buy a transit card (COP$4,000) and load it with money (COP$2,100/trip; going up to COP$2,300 in 2018) in order to use it. More than one person can use a single card for a trip. Feeder buses for this system include buses to the airport and to Bocagrande.
You will still see the older, more colorful local “busetas” which stop if you flag them down; fare is COP$2,100 (cash; change will be provided for small bills). Destinations are written on the front of the bus and are called out by the ‘Esparring’ (bus assistant), but it can be confusing so don’t hesitate to ask! Let them know where you’d like to get off & they will stop.
You will see a lot of (mainly) men on motorcycles carrying an extra helmet; they are looking for paying passengers. While technically not legal, a blind eye is turned. This type of transportation is not recommended!