Banco de la República, on Carrera 7, exchanges cash at good rates. It is open weekdays 9-3. Several banks on Carrera 10 around the Hotel Tequendama also handle foreign currency. Your hotel is probably the most convenient place to exchange money, although it will charge a higher fee. ATMs are located around the city, clustering around the Centro Internacional and inside the shopping centers in north Bogotá. They are on both the Cirrus and Plus networks; you don't need a 4-digit PIN number here -- a PIN of any length should work.
Banco de la República (Carrera 7 No. 14-78).