Spent a few weeks there 2 years ago traveling the entire island. Found a few spots but didn't get off anything, not for the lack of trying though. One 'B' in particular was relatively easy to access but the LZ's were tight! Other 'B's were a bit more difficult to get to the roof. The winds there may be an issue as Havana is on the coast.
There are a few other sites around the island that you might be able to jump but they are not ideal to say the least. There is a bridge that has no LZ, a few low antennas and a couple of smokestacks that have no ladders or ones that are rusting through. Oh, there's also a shitty low, rusting, crumbling light tower near a stadium I climbed up. Lucky I didn't die on that one!
There are always people watching you so it's a bit difficult to scope objects. Renting a car to get around outside the city is a chore and very costly btw.
Maybe someday I'll make it back and get a jump... maybe not