French is the official language of French Guiana, although Creole is widely spoken. The majority of the population speaks French while few understand English. However, some officials, police, and gendarmes may speak English. Because of the presence of many Brazilians and Dominicans, many people understand basic Portuguese and basic Spanish. On the Maroni river, Taki-taki is often used.
Being so far away from metropolitan France, it is often forgotten that the Guianese are, as well as a distinct people in their own right, also French citizens. Don't let them seem either one of those too much, they are in between and value both their own culture and their French citizenship.