We were registered Democrats our entire lives, until Trump became President. We quickly learned that we were on the wrong side of life (although we consider ourselves moderate conservative, we are pro-choice and are not hardcore religious...but that's a subject for another day). We instantly became Trump fans...and we're Mexican/American! I was informed that if we're independent, we can't vote for a Republican Presidential nominee. So, do we have to register as Republicans in order to vote for Trump?
Edit: Forgot to add we are in California!
In most states, you can only vote in the primary (which selects the candidate for each party) for the party you are registered as belonging to (though in a lot of states, it's easy to change your party registration just for the primary, and then change it back again). But in the general election, when the actual winners of the various offices are chosen, any registered voter can vote for any candidate.
The states which have open primaries (meaning any registered voter can vote for any candidate, regardless of party affilitation) are: Alabama, Arkansas, Georgia, Hawaii, Michigan, Minnesota, Mississippi, Missouri, Montana, North Dakota, South Carolina, Texas, Vermont, Virginia, and Wisconsin https://www.ncsl.org/research/elections-and-campaigns/primary-types.aspx But all of those states have already had their presidential primaries (some states have separate primaries for President and for state offices).
That's not quite the case in Michigan. You don't have to declare and aren't asked your party, but you can't split your ticket in the primary. If you vote for any Republican, you can only cast or withhold votes for Republican candidates and vice versa or the ballot will be counted as spoiled.