Spanish is the official language of Cuba and is spoken throughout the Island. English is spoken by Cubans in many of the tourist areas such as Varadero, and in the more prestigious hotels in Havana and other large cities. However, once away from the tourist areas it is hard to function without some knowledge of Spanish.
Many Cuban business people understand and speak English, but in most cases foreigners make a greater impact anf find more acceptability if they address themselves in Spanish to their Cuban interlocutors.
Use your international mobile phone rental to find a translation service near you.