Jacareí can offer a decent amount of safety for solo female travelers. Like any other location, it is important to take precautions especially at night and in less crowded areas. It is advised to stay in well-known and frequented areas, also avoid participating in risky behaviors such as accepting unsolicited offers from strangers. Public transport is reliable however it's better to avoid it during late hours. Though petty theft and pickpocketing are common in crowded areas, violent crime is relatively less common. Familiarize yourself with local customs and know enough Portuguese to ask for help if necessary. Stay alert, but enjoy your journey.