Like is most major cities the most common crime reported by tourists is theft. Opportunists are not normally violent but will try to get cash or valuables from your person. Take extra care in busy areas like the metro, trains, buses and shopping areas where there are large crowds and busy people.
Public transportation is usually considered to be safe and reliable, although there are occasionally reports of youth gangs accosting passengers on trains during the summer.
When parking, especially in rental cars and vehicles that are clearly from out of town or foreign, always remove any visible personal belongings. These types of vehicles are frequently targeted for break-ins, especially as they are usually parked in popular tourist areas and beaches.