Hi Miss Jessie,
Northern Queensland is a nice place, just wouldn't want to live there. The summer months will drive you mental. Oppressive heat and insane humidity.
Not a big fan of Yorkeys, as others have commented, muddy water, no swell, choppy. The mozzies at dusk can literally pick you up and carry you away

As a town, it's full of tourists and backpackers. This means cheap eats and a younger crowd. On the plus side it has a cable park! There is really only one beach to kite at and not much variety in conditions. Locals were friendly last time I was there (long time ago).
Port Douglas is a different crowd, less backpackers, more rich tourists. The local council doesn't like you if you don't have money to spend. PD is expensive and not a lot to do other than kite and maybe mountain bike. Wind can be hit and miss in an off season, and can be great in a good season. You'll need bigger kites than WA. Water is same muddy stuff as Cairns along the coast but cleans up beautifully off the coast.
Not lots of options for variety in PD either with regard to kiting unless you jump in with Bretto and do outer reefs etc. smooth water though and pretty fun. Relaxed crew with loads of blow ins.
Cooktown is epic windy, being north of the GDR it gets true strong trades funnelled along the landscape which provides strong wind, rolling sea chop which breaks and acts like surf (onshore). Crocks are a bit of a worry at Cooktown. Sleepy little place with little to do but people are the friendliest in Oz.

I rate it!
Townsville has a great variety of riding locations both around town and also within an hours drive north or south. Epic flat water, steady breeze, great town, plenty to do.
Stinger suits are a good idea for the stinger months but luckily the stingers only really come to the surface when the water is calm ie no wind, and dive deeper when it is choppy so you are less likely to encounter one when kiting. It's still strongly adviseable to get a stinger suit in case you run into an irikanji or Boxy.
My pick would be Townsville, but I have a few good mates in town which makes it all the more attractive for me. For a girl, Townsville has to be a good place to look for a bloke as every night club is a sausage party with the Army and AF in town.
Have fun and good luck, you really can't go wrong, they are all 100 times better than Canberra!
DM