Not sure how you will adjust to the warn water diving, that is all I have ever done, and I do get cold easily. If I am doing a lot of diving in the warm water I will get cold and have to wear a 3m shorty. I would ask the dive op if they have any suits you can rent, most ops I have dove with do but Tintipan looks like a pretty remote place so they may not have an ample supply of diver to sustain rental equipment.
I’ve never been to Medellin but I know it is know for it beautiful women.
Cartagena is a beautiful city, some parts, if you like old city and artsy culture you will love the fort, forgot the name. I have heard since it became a heritage site they have fixed up a lot of the run down places, real-estate prices have skyrocketed and they have cleaned up the poverty and panhandlers inside and around the walls of the fort. I can wait to go back. The biggest down fall to Cartagena I found is there’s a lot of poverty so you will get mobbed with panhandlers trying to sell you everything from sunglasses to candy, almost anywhere you go.
ciao
Tad