French Guiana is a country in South America. Even the Lonely Planet says that hitchhiking is doable, so unlike the former British colony Guyana (which is considered rather unsafe), you can stick out your thumb without too much worries. Wisdomseeker has hitchhiked in French Guiana - it is certainly 'doable'. It is generally a safe country (technically an overseas department of France). Naturally, it helps if you can speak French.