first, know that every country here has its own accent, sometimes multiple ones like us. and mexican accent would sound weird to them. you could start with basic shit to order food, ask for directions or general chat. then aim for the words you will use at your work more often, the proper names of tools and parts. screwdriver here "destornillador", and there are not shorter words for it.  repairing farm equipment is quite the job here, not saying you'll become rich, but the farmers here are always breaking shit up. and they do not have the money to just buy new tractors or harvesters. you'll never ran out of work. also it could happen that shallow people would hire you before "juan lpez" cuz you a "gringo" and therefore better.
Argentina