There are regular flights to Resistencia airport from Buenos Aires Aeroparque airport.
Flying into Corrientes airport is also an option. There are buses from Corrientes airport to Resistencia.
Being a central hub for the Chaco country, the bus terminal in Resistencia has many connections per day with Buenos Aires (12 hours), Rosario (10 hours), Puerto Iguazú (12 hours), Salta (13 hours) and Asunción in Paraguay (6 hours). Lesser served routes (ie. once per day) include Córdoba, Posadas and Rosario. There are numerous local buses to the neighbouring town of Corrientes and the National Park Chaco. The bus terminal is located outside the town center.
A coach from Salta takes about 12 hours and costs about 80 pesos, however it is difficult to get one at sensible hours, ie you have to either leave stupidly early or arrive stupidly early, the best I could find was 6pm - 6am, and the bus was an hour late, which suited me fine.
Hotel Luxor a cheap hotel (23 pesos without breakfast) only a few blocks from the plaza.
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