Palma
Is the main shopping street. pretty much everything you can buy here, you can get cheaper in one of the parallel streets.
Traveller Cheques
American Express Traveller Cheques can be changed at Banco de la Nacion Argentina at Plaza de los Heroes. Above average exchange rate, 3 US$ comission. It will take a while though - time to experience the place which could be a sight in itself. BBVN supposedly does as well. Casa de Cambios don't. All banks close by 1:30PM. Also can be changed at Maxicambios (http://www.maxicambios.co...) which are located in all main shopping-malls.
The cost of buying goods and services is cheap. This is only partly due to the fact that Paraguay is a piracy and smuggling haven. Be aware that some goods may be cheaply made.
Indigenous crafts and artisan work are available such as tooled leather, carved wood, pottery and a particularly Paraguayan lace based on a spider's web called "Ãanduti". Check out the artisan shops in Plaza de los Heroes. Most goods are in fact locally made.
Shopping malls There are two main malls in Asuncion Shopping del Sol on Aviadores del Chaco and Shopping Mariscal López on Avenida Mariscal Lopez, exist in the suburbs of Villa Mora and Carmelitas. Take buses 28 or 30 to reach them. Mall Excelsior on Chile, and the more basic Asuncion Supercentro on the western end of Oliva are both in the centre. These "Shoppings" are useful as places to eat on Sunday evenings, when many more central places are closed.
Mercado 4 along Avenida Sivio Pettirossi, is a chaotic market where you can buy just about anything very cheaply, it is particularly good for counterfeit clothing and pirated CDs and DVDs of varying quality. Good street food and some foreign, mostly Chinese, restaurants.
Typical souvenirs from Asunción would include guampas/bombillas, t-shirts, traditional lace, or leather goods.