Wash and straighten before you go for sure. Since you have longer hair, I'd keep it French braided, in a pony-tail, or pig tails for control (both bugs and humidity). As other's have said, a cute ball cap during the day might be a nice touch and an easy weather protectant as well if it should rain or be waaay too sunny and hot.
For emergency-sake, you may still want to bring along a good brush, hair binders or a clip, and one styling product anyway. For instance, a leave-in anti-frizz serum (any products with Moraccan Argon oil are great, but perfumey!), curl pudding (Miss Jesse's at Target is great for controlled natural looks!) or some type of leave-in conditioner/cream (I like John Frieda) to get things under control if humidity is a problem and you need to tidy up, or you wind up having to get your hair wet anyway. You wouldn't want to go unprepared if something unexpected should happen. But I definitely think going into it with straightened hair would be waaay easier than messing with the curls while on the trip.