We went there in January 2011. We stayed in Negril for 7 days and then stayed in Runaway Bay for 3 days.
We could not do the day trip from Negril and back in one day. Your looking at a 12 hr day if the weather is good.
I do know a couple of girls that went while were in Negril and Ernie took them in a day trip. Ernie is stationed out of Country Country.
I don't know what company he is with but he took us to Pelican Bar and he is terrific!
I would go back to Nine Mile again! It was a prety cool trip!