I’m a new rider myself, so take my 2 cents with a grain of salt…
I would try to practice on a bike that’s in the same class as the one I would be getting. If you’re going to get a sport bike, practice on a sports bike. If you can practice on the same model bike you’re planning to get even better.
I didn’t get a Ninja 250, 2008 or otherwise as I opted to go for a ’07 SV650SF ABS, but I have a more experienced friend with a 2006 Ninja 250 and a coworker who got a ’08 Ninja 250 and they both let me ride their bikes once in parking lots. I liked riding both of them. I can’t tell the difference really between the 2 as there wasn’t much opening up in a smallish parking lot, but the Ninja 250s in general seem to be very forgiving and very comfortable rides.
For me, there was a big difference in feel from riding the cruiser bikes at the MSF and mine and my friends’s bikes. This could just be from me being a new rider and my riding skills not being polished compared to more experienced riders.
Oh and FYI, according to the Hurt study, “… riders taught by friends or family were are about a third more likely to crash than those who taught themselves” – Proficient Motorcycling, David L. Hough
An interesting book, great read, and interesting stats and info. I recommend it. But I’m not saying don’t get your friend’s opinion on things or to teach yourself. 
Anyhoo, good luck in your endevours and have fun!
If there’s anything more important than my ego
around, I want it caught and shot now…
