best cuban sandwich in Miami?
I'm not sure it qualifies as the best Cuban sandwich in Miami, but you can get a more-than-decent one downtown at Latin House which is on Flagler St. near Miami Avenue. There are several other Cuban places along Flagler whose names I will never remember but all of which will probably do a passable version.
I think you can walk to the Latin American Cafeteria in Bayside, which is a pleasant, albeit cheesy, Rouse type shopping area for middle to low-end tourists, if you'll forgive my condescension. It is by the water so that works. They've always made a reasonably good Cuban sandwich. Los Ranchos is there along with The Knife, so you can get a bit of Nicaragua and Argentina as well. Finally, they have a cheap food court as well.