Navona perhaps 15 or 20 minutes depending on how much you dawdle. You could walk to Pza. Venezia in about 15 minutes, perhaps 20, which puts you right at the historic Roman center. Though ordinarily we'd use a bus which only takes 10 minutes, more or less depending on traffic. You can find a 2-star in Rome for about twice as much, but don't expect to find an equivalent room.
Rooms are usually smaller, less brightly lighted and perhaps somewhat less well furnished.
In cities you may find more noise. Air conditioning is not common, even in Rome, except at more expensive hotels. Even some of the better properties are below expected standards. Your neighborhood bar or caffe is often the best choice for a 'continental' breakfast. Prices lower if you stand, higher at a table.