Barjouville lies in the Beauce plain just south of Chartres, where standard metropolitan French is spoken in shops, at the mairie, on regional buses, and in the small hotels that serve the area. There is no regional dialect or minority language to worry about, but the local Centre-Val de Loire accent rounds the classic French 'eu' vowel and slightly softens some open vowels — easy to follow once you are tuned in.
Because Barjouville is residential rather than touristic, English is far less commonly understood than in central Paris or the Chartres cathedral precinct. Opening every interaction with 'Bonjour,' finishing with 'Merci, bonne journée,' and slotting in 'S'il vous plaît' will carry you through the bakery, the taxi rank, the regional bus to Chartres, and the small hotel reception without difficulty.