Answer
Safety is better assessed based not on an area's name but on the specific address and routes. Even within Montevideo, neighbouring neighbourhoods can differ in lighting, pedestrian traffic, public transport, the condition of buildings, and the level of day-to-day risk.
Before renting, it is worth visiting the property in the morning, in the evening, and on a weekend; walking the route from the stop; and checking for shops, lighting, windows open onto the street, and vehicle traffic. An empty street at night and a busy avenue during the day are different environments. Areas with little traffic and poor lighting require extra caution.
It is useful to talk to neighbours, nearby shop owners, and people who live nearby permanently. They can better advise you on where not to walk with your phone in your hand, where cars are parked, and how the situation changes in the evening. The decision about an address should be based on this everyday picture.