Semi-formal. No shorts or sandals please, but we recommend wearing lightweight clothing.

We recommend arranging transportation through your hotel for pickup. If not, then you can call an uber when you exit the terminal. Uber is recommended over taxis so you don't have to negotiate a price.

Uber! Uber is a great option. There are lots of drivers and it is easy to get a ride. If you are staying in the Old City most of the events and sights are accessible by foot as well.

Credit cards are accepted most everywhere (restaurants, shops, etc.). You might want to get some Colombian pesos for buying food from street vendors or in case you have to pay for a taxi.

Yes, Colombia is very safe. We have visited a number of times without any issue. Cartagena is a big cruise ship destination, and the area we are staying in is very touristy and safe.

No you do not need a visa to enter Colombia. Just don't forget your passport.

No you do not.

Cartagena is tropical so expect it to be warm and humid. We recommend packing linen, and other lightweight clothing.