Upon our arrival, my wife, my 10 m/o son, and I all stayed at a great little B&B that recently opened called El Jardin de Montserrat. We truly loved it, as we stayed there for all of February. The setting was so "tranquilo" and the family running it was so helpful that we've stayed close friends since moving out at the end of the month into our new house.
PERFECT for extended stays or regular weekend stays. Totally affordable, with the most expensive room being the poolside suite with a bedroom, living room, small kitchenette, and breakfast all included.
Here is my wife's review of the place on our website, called "Welcome to Paraguay: Our Stay at El Jardin de Montserrat."
And here is my review on TripAdvisor of the same place.