The truth is that local transportation is pretty irrelevant around the actual city of Posadas. Everything of interest is accessible on foot. City buses do run, but are more likely to get you lost than to save you time. The Playita (little beach) and Plaza 9 de Julio are about as far about as any two places in town and it will take about 20 minutes to walk between them. There are plenty of ups and downs however and when cutting through town expect to climb some hills. The Costanera stretches for a few kilometers and may be the longest route to get around but it is an interesting walk, never boring and usually helps to orientate. Taxis are available if you are too sun baked to wander.