The rate can change from day by day. For the time being the rate is about 2,5 real for 1 euro. The banks are open from monday to friday from 10.00 to 16.00.
On the boulevard of Ponta Negra is the bank usually only open in the afternoon. You can also exchange cash. In Brazil you can easily withdraw money with your credit card. There is a daily maximum. Please enquire in advance at your bank how much that is and make sure that your pass is registered at your bank to do transactions outside Europe.
Keep also note that there are often breakdowns. In Praia and Natal Shopping and in Midway Mall there are ATM machines to find from Banco do Brasil and open until 10 in the evening.