is possible to use 2 or 3 different simbol currency for example for 4 countries: USA = $ Dollar Guatemala: Q. Sweden: Kr. England: £
There isn't anything built in to support multiple currencies at the same time. That would bring up several different issues first of which I think would be confusion for the end users.
This is a long thread but discusses a lot of the issues with multiple currencies. http://www.68classifieds.com/forums/technical-support/7817-hw-change.html
Yes but I wonder that, because I have customer from Guatemala its currency is Q. Quezales Venezuela is Bolivares, Peru is Sol, Honduras Lempira, etc. and they asking for a change rate, and I dont know. It is assumed that the system ADS is not for a single area and thus brings the list of countries. I dont know, will be better not to use a single curriency for your ads. other people likes to see ads from the same area. Or build a module for Change rate, it will be important I will buy it.
There are several to choose from - just type forex into google - many companies offer a free convertor because people may then run through to use their services.