There is a good article linked from FAS about Cuban Missile Crisis,
It talks about Short Range Nuclear Missiles that US did not know about during the Cuban Missile Crisis. According to the article there is about 12 FROG missiles and 80 FKR-1 missiles ready, along SS-4 and SS-5 which only 6-8 were made operational during crisis.
Well, SS-4s and SS-5s could reach mainland USA with no problem. However on the other hand, FKR-1 missile and FROG missiles had the furthest range of 100 kms. That can't even reach Key West from Cuba. I linked my sources below, maybe I looked at the wrong source and the missiles have longer range.
I don't know that much about the Crisis, but I believe the invasion of the islands were considered seriously at least at some point. Do you think if US knew the presence of these short range nuclear missiles would, they still consider invading the island ? I think the only purpose of bringing in these missiles is to prevent an invasion rather than being used as an offensive weapon.
THE ARTICLE : The Cuban Missile Crisis: A nuclear order of battle, October and November 1962
or could be reached from Federation of American Scientists
also there is a mention from miami herald as well The untold story of the Cuban Missile Crisis - Latest News - MiamiHerald.com
FKR-1 MISSILE : Soviet Surface-to-Surface (Coastal) Missiles
FROG MISSILE : 9K52 Luna-M - Wikipedia, the free encyclopedia