There are plenty of banks and money exchange companies in downtown Asuncion and the Villa Morra area.  So if you need to change money just go to the commercial area in the city centre of Asuncion or any shopping centre in Villa Morra.

For ATM machines there are even more options.  In Paraguay, the financial sector is dominated by cooperatives (33%) finance companies and banks.  All of them have got ATM machines in their branches so you will never be far away of one if you move around the commercial areas of the city.

Exchange rate is about 1 euro x 7,000 Guaranies; 1 pound x 10,000 G. and 1 USD x 5,400 G.  For up to date values, you can check on http://www.cambioschaco.com.py/index....

It is better if you keep only small ammounts of money on you and you use debit (Maestro, Visa electron) or Credit Cards for your shopping as they are widely accepted.