Hi there,
I have the same problem as I have REALLY curly hair that frizzes up as soon as I set foot in Orlando!! The first time I went to FL I managed to blow up my very expensive hair straighteners, so I went to Walmart and bought the most expensive pair in the store. They are rubbish in comparison to GHD's and they don't straighten it half as well and it still starts to frizz went it's really humid.
This year I tried something else for the first time that I have now become addicted to and will never set foot in Florida without having it done again!
I went to the hairdressers and had a Keratin treatment done which was BRILLIANT!! It was expensive as I had one done that lasts 3-4 months but you can get one done that lasts just a few weeks. It straightens your hair, makes it MUCH more manageable and makes it really glossy. Apparently it's what Kate Middleton has done to her hair, that's why you never see it frizzing when she's about and about like it used to when you see her in old Uni photo's!!
The treatment that I had, you have to go into the salon have it put on your hair, then you can't get it wet or put it behind your ears for 72 hours (which was difficult), then you go back for the second part, so if you are considering this then allow enough time before you go away.
Once I had it done it was fantastic, I got caught in the rain a few times and it still stayed really straight and didn't frizz once either in Orlando or in the Bahamas when we went cruising on the Disney Dream. It took half the amount of time to dry and no styling - BRILLIANT!!
You do need to use the Keratin products afterwards though as normal shampoo strips it off and it won't last as long. The hairdressers gave me travel samples included in the price but I also bought shampoo and conditioner at Walmart to bring home as it was much cheaper.
Just an idea, but I thought I'd let you know about it and how pleased I was with it. Like I said it is exepensive (I paid £200 for the one that lasts the longest, but you can get one that will last you for the holiday for about £45 I think), may be worth a try, but beware you'll become addicted!!!
Jave a great trip!