Best place to farm is to go up and down on the spawns to the right.
As for the drop rate, it's just heavy RNG, for example I got about 17 bananas in the time it took my guildmate to get 7, when we farmed together for about 60-75 minutes.
Note that you can always see the spawn locations of the related mobs using the data on this page: Dropped by NPC tab - Click NPC name and see it's locations.