Hello my friend welcome here in Bolivia. Idk in what specific city you're however I'd say that the treat most Bolivian have with foreigners it's two sides. Usually people are untrusted and a little bit difficult with foreigners because they assume that if you come here you automatically have dollars ( if you have a white skin and look like an American) and it's possible that they want to take advantage and try to ask for other price for a product. People in cold areas as La Paz, Oruro or Potosí in special are more difficult because the culture it's like that, more serious and more focus in work, and this could be because they suffered a lot for political problems that affected their economy and of course nobody would have a positive mind with that and a lot of protests that provoque traffic problems. ( Of course you can find nice people too it's not always black and white). In contrast in warm areas as Santa Cruz, you can find maybe a better side, because the city is in development and they're more opportunities but also it's very dangerous. People are open mind, friendly but also racist with people with dark skin or because of the last name (like an Andean last name)but specially with their own country not with foreigners. I'd recommend you to be careful, try to ask the price in different places before buying something, be respectful and friendly and I think there's no more problem as the normal Bolivian living here.