Lots of well meaning advice here, but for someone who wants to revise from gastric bypass to DS, Mexico is not an option. Dr. Esquerra does revisions of lap band and sleeve to DS, but not RNY to DS. Even if there is some other surgeon in Mexico for offers this, I would not recommend anyone go there for this very complex and higher risk surgery, especially to a surgeon with less DS experience.
Now, if the OP wants some kind of simpler gastric bypass revision, such as proximal to distal, there are probably surgeons in Mexico who do this, though I don't know who they are. But this type of revision is unlikely to create significant weight loss.
Sorry!