The names of many streets have changed over time, but many locals use the old familiar names.
For example, you will hear them say Galiano but if you glance up at the buildings themselves, you will see Avenida de Italia has been carved upon them.
If you use a Havana map, you'll have less confusion about street names.
Carry a map of the city that shows both street names
Reina was renamed Avenida Simon Bolivar
Carlos III was renamed Avenida Salvador Allende
Belascoain was renamed Padre Varela
Monte was renamed Maximo Gomez
Zulueta was renamed Agramonte
Malecon was renamed Avenida Antonio Maceo
Vives was renamed Avenida de Espana
Galiano was renamed Avenida de Italia
Teniente Rey was renamed Brasil
Paseo del Prado was renamed Paseo de Marti
A few years back it was difficult to find a map of Havana but now the tourist kiosks in Old Havana, and many better hotels, sell large fold-out maps for a reasonable price.
You will find these invaluable in making your way through the winding streets.