Hi again people, today I bought a 3G Mobile BroadBand USB modem from Telcel (Mexican Company) and here are my experience.
1.- It was very easy to set-up the the 3G USB modem, you just need to have the NetworkManager (last version is 0.8) updated, if you don't have the NetworkManager download it from your repository (I think 90% of the distros has this app on they repositories, but if not) download it here.
2.- Plug your USB Modem and right click on the NetworkManager icon (top-> right) and select "Edit Connections" and then go to the Mobile Broadband tab and click on the "Add" button
3.- Follow the wizard, select your country, your service provider and your plan (most of the providers don't have a plan, so select the default)
4.- and you are done. now you can enjoy your 3G wireless connection.
Any question or comments are welcome. If you have any other distro or need help, I'll be happy to help you, just ask me. Thanks
EDIT: for some reason you need to eject the USB disk move before use it, otherwise it'll no work, I'll check it and come back with a solution ASAP.
Source: Voices in my head