This is an okay option - and a decent price for the location.
Note - except for the fanciest hotels - it is likely that you will not have hot (or warm) water in your hotel. Calamari does not have hot/warm water. Apparently this is typical for many buildings in Cartagena.
The best part of this place is the location - it is in the old town center - and right near one of the entrances gates to the city.
The worst part of my stay was the room - The size of the room was nice, but it was very dark. And my room had no window!
Also - I booked my room through hotels dot com and the room was advertised as having a private 'furnished balcony' - obviously this was not the case as I did not even have a window. When I brought this discrepancy to the staff's attention - they just said that 'no, that is not possible, your room does not have that.' There was no attempt to offer a discount, or room switch, or even to apologize.
I arrived before check in - and they don't have a room to store your bags - you just have to leave it in a public hallway.
Not sure why people are calling this place a hostel. In Spanish they refer to it as a hostal, which is not the same as hostel. Anyway, it's a hotel - and the prices are certainly hotel prices, not hostel ones.
However, for the price and based on the reviews, I was expecting something really amazing.
Don't get me wrong, this place is fine, and the location is perfect. But just don't get your hopes up.