I've been to Jungle recently a few times and I don't find they play much dancehall at all - more like regular dance music. There are different places around Negril that have live reggae music on different nights... Roots usually has music, Drifters does on certain days, Alfreds, Boat Bar (in season)... but dancehall is less common. Yard bar might be the closest to the dancehall experience that I've seen (but be careful!). When you're in Negril, ask around at your hotel (or a local guide) to find out where/when the music is that week.