Choosing a country: Crime Index
Will you be safe in the city? It is important to realize that every city has crime. The important questions are: What type of crime is most common? Who are the most common targets? What can you do to reduce your likelihood of being a victim of crime?
In general, Costa Rica has the lowest Crime Index of Central America. Like in every big city, San Jose also knows crimes. However, big crimes like rapes and murders hardly occur. Petty theft is what you have to be careful with, especially in the downtown area. Obviously, common sense can prevent pickpockets from taking your precious belongings. Do not wear a lot of jewelry and never leave valuable stuff out in the open. Prevent the visibility of your belongings (Keys, phones, watches, laptops, basically anything you are not comfortable losing) in your car, your hotel room and when eating out, never leave your wallet etc. on the table. When going out, you should never take your real passport with you. Make sure to get a copy of the main page with your photo and personal information and a copy of the page with a stamp of your entry to Costa Rica. When asked for identification (by police or in a club), these copies will be sufficient.
As San Jose is a big city, there are a lot of different neighborhoods. Most of these neighborhoods are pretty safe, but use common sense when walking around. Before going out, ask your neighbors or people who are familiar with the area what they think about the risks.