Do Haïtians from Port-au-Prince completely understand everything that a Haïtian from the north or south of Haïti is saying? Will it be difficult for them to understand their accent and words?

Men wi! tout Ayisyen kèlkeswa kote yo sòti, nan Lès, Lwès, Nò oubyen Sid Dayiti va konprann Kreyòl ki pale  .....depi se Kreyòl Ayisyen l ye. Aksan moun nan Nò oubyen nan Sid p'ap anpeche w swiv yon konvèsasyon nonplis. Gen de twa mo vokabilè ki ka pa menm nan Nò ak nan Sid - donk si w tande yon mo ou pa konprann pran plis enfòmasyon sou mo a.
Absolutely! All Haitians whatever their origin, East, West, North of South of Haiti, will understand spoken Creole ...as long as it is Haitian Creole. Northern or southern Haitian Creole accents won't prevent you from following a conversation. Some vocabulary words may not be the same in the North and South, so ask about these words if you hear them.

Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words