Oswald - Cuban Connection

I just saw a documentary last night about the possible connection of the Cuban Secret Service (G-2 I think they called) with Oswald. They interviewed a few Secret Service Cubans and some denied it and some confirmed it. Also interviewed were some people that used to work for the Cuban Embassy in Mexico around the JFK period and they were saying that Oswald was very active there in the lead up to the assisination. I was wondering if anyone knew how strong this theory was with this connection or is it all just speculation and a load of bulls**t?