The Hispanic vote varies in composition from state to state. The Hispanic vote in New York is mainly Puerto Rican while in Florida it is mainly Cuban. When the term Hispanic vote is used, it is usually thought to mean Mexican. Donald Trump has promised a wall on our southern border to keep all those undocumented (Mexican) people out. If Trump cites polls showing Hispanic support, he is talking about Florida where the Hispanic (Cuban) population is more conservative than Hispanics in general. One way to think of it is the conservatives in Cuba have emigrated to the US, while the liberals have stayed in Cuba.
Trump wants a wall on our southern border, but he has not and will not propose a wall around Florida to keep out the undocumented. The fact that a wall around Florida would help prevent flooding from a rising ocean is another reason that the GOP would not support a wall there. The GOP don’t believe that the oceans are rising and would do nothing to prevent it if they did.