All Cuban cities are quite safe as they are relatively free from the well-known street dangers encountered in other countries. The Cuban people themselves and travelers can equally walk the cities and streets day and night without having to be concerned about criminal behavior.
Purse snatching and mugging are not unknown but are rare in the extreme and pose no problem for anyone with minimal street smarts. In major cities a friendly police officer can be found fairly quickly, and in tourist areas there is probably one on the next corner.
Care should be taken against pickpockets in crowded places like public buses, discos, bars and theaters. Still, few travelers to Cuba will likely experience anything more than the nuisance of an occasional peddler of artifacts or a young hustler wanting to be your guide.
Cuba is extremely safe by any world standards, and the average visitor has no reason to worry about personal safety on the streets, in the hotels, at the beaches or any other place a traveler might visit.