Luis, I would check out OpenBravo as a free open source ERP system. I played with it a little as a product engineer at my current company. Unfortunately I did not realize our company was looking into something and chose a different product that seems to be not as user friendly. It is free to try with a "VM" as a download and does not require an installation to test it. Another good thing about that product is that it is backed by a real company, so if you can work on implementations, customizations, and your customers have the option of purchasing support through "Spanish" based developing company. Good Luck with your search, Tim