It all Depends man.Some Jamaican's Probably Grow Shwagg while some probably Grow some insane Organic blueberry Skunk!
If it is actually from jamaica there's a good chance that it will be sativa dominant.On the other hand it might be indica as lots of young Jamaican's are growing indica's for the faster season.
In this Documentary I Recently Watched this young Jamaican was growing Blueberry and skunk and some other indica Dominant Hybrids,This allowed him to have a crop every 60 Days,
He Said he get's 6 crops a year.
But It might not even be from Jamaica,it could be the name of the strain...I had a very Good Sativa a while back called Jamaican Sugar.and I'm positive it wasn'y from Jamaica.(It was at least AA Quality.)Perhaps one of the original parents used to create the strain was Jamaican.