Where are you planning to go in Paraguay, and for how long? If you're just in Asunción for a few days, I can't imagine why you'd need a driver. If you're planning to travel around the country for a while, that would be different.

If you're just staying in Asunción, most everything you'd want to see is in the city center, which is very walkable. The bus system is also quite easy, assuming you speak enough Spanish to be able to ask for directions and the like.