Castro was a smart man in that regard and on top of it, with the help of a surprisingly efficient and vigilant security network as well as comprehensive Soviet intelligence, he thwarted every assassination attempt on his life (which is reported to have been over 600). He seemed to have taken it personally though; he constantly demanded Khrushchev nuke the US, which really horrified him, so he made sure every single battlefield tactical nuke was removed from Cuba after he and JFK came to an understanding. I personally believe not all of them were and the Cubans were perfectly capable of losing them for a while until they could make dummy replacements. Or maybe the Soviets went along with it because after the Bay of Pigs the US has never tried to invade again. You can't convince me Iraq and Syria are easier targets than an island 90 miles away from Florida populated by a bunch of Cubans either addled by the hot sun or pissed off at the Castros because Axe spray, tight jeans and decent hair relaxers are unavailable.