Florida is a closed-primary state.
Voters registered as Republicans may participate in the Republican presidential preference primary.
Voters registered as Democrats may participate in the Democratic presidential preference primary.
Voters registered as independents may not participate in either presidential preference primary. Independents may vote in local nonpartisan elections, such as the one taking place in Surfside today.
I suspect Donald Trump knows the facts but prefers to add a few logs of his own to the fire. He is, in fact, no dummy.
Donald Trump's Epic Neediness, by Frank Bruni. (The New York Times, 3/12/2016)