My first car (2001 civic) was an automatic. I wished it was manual, and hondas are easy to learn on.
My second car (1997 240sx) was an automatic. After 2 weeks of owning it, I parked it in my parent's garage, took out the automatic slushbox and put in a 5 speed manual. The car felt totally different - I was much more in control, the car was much faster, and the car was much more responsive. I still own this car and it is a blast to drive.
I own 3 other vehicles. A (1959 Morgan +4) a (2004 Kawasaki Ninja) and of course my (2011 Z) All of which are manual. I personally think a sporty car needs a manual and I much prefer driving a manual even in traffic. The Z's transmission isn't the smoothest and the clutch is kind of a pain in the butt but it's lightyears easier to drive than my Morgan - which doesn't have synchros, or my 240 which has a crazy stiff clutch. The Z with the sport package also helps smooth out your shifts when you're first learning with it's synchro-rev-matching (SRM).
As far as the Z not being a good car to learn stick on:
The shifting isn't bad, I taught one of my good friends to drive a manual in my Z last week. She stalled a few times in the parkinglot, but then drove it about 50 miles around town at 4:00am with no real issues. She had never driven a stickshift.
However, I would never let my future children have the Z as their first car. It is FAST and it has a temptation to GO FAST. With new drivers, this means you DIE FAST. I think manual transmissions easily get out from under new drivers, this coupled with a powerful engine and rear wheel drive make the car a bit of a handful for new drivers. If you are responsible it would be an okay first car (albeit very expensive for a first car). A kid when I was in high school got a Dodge Viper for his first car
and he managed to roll it. Remember that if you want to go fast in it go to a track or autocross - and since you're in highschool you will need one of your parents to go with you to sign a waiver.
In conclusion: I wouldn't recommend it as a first car. I'd get something else like a stickshift civic or even miata (which is fuuun car!) and leave a Z for later once you are a more experienced driver. The Z is an AMAZING car though. Probably not what you wanted to hear, but just looking out for you and I'm not trying to sound like I'm the best driver out there either. Just my .02$