I have never had any luck with drip irrigation on either small or large scales for bananas - they tend to get rotted out or starved and as somebody astutely pointed out it's very hard to get total root system watering with a drip system.
A well is a very good idea, as is a rainwater catchment system that you can pump through your sprayers in the dry times - this is what I ended up doing when I had about a hectare of mixed bananas in the Ecuadorean high altitude desert, and it worked like a charm except when earthquakes disrupted my tubing system - then I had to water all those nanners by hand...
