We arrived to Valletta to see the carnival, and we found that the apartment is beautifully located 5 minutes from the Valletta main street, were all the action took place. Everything is nearby (main street, nice restaurants, shops). However, If you are not in a good shape, the first two days might be a bit difficult because you have to climb 100 meters up hill.
The location also allowed us to experience the life of the local people; the building is quite ancient (although the apartment is maintained and equipped very well, and also very cozy), a small grocery store is in a one minute walking distance, and a very good pizzeria in 3 minutes distance. You could view the entire street from the windows, and you may hear the traffic on the street at the morning.