I don't speak Spanish, but I'm an experienced developer and extension development does not depend on language. I've checked MercadoPago API documentation and I believe I can develop that payment extension for you. I have already rewrote couple of plugins, for example for AsMoney, 2000charge. I have also developed some other OpenCart plugins. If you don't agree to the price or the time needed, I'd love to hear your thoughts. Please contact me to discuss project details. I guarantee that the work will be done in the best quality and on time. As well, during the development of the project I will always be available via e-mail and Skype.