Mont-de-Marsan is generally safe place to travel for solo female travelers. As with any other place, it's important to stay mindful of your surroundings, especially during the night or in less frequented areas. French people are usually friendly and helpful. Aggressive crime is rare, though minor thefts can occasionally occur, so keep an eye on your belongings. Public transportation and walking around the city is generally safe. However, always remember, safety can largely depend on your actions, behavior and awareness.