I'd never sell my little ninja...
Some say u'll get bored of the 250 in a few months and want to move up:rolleyes ... That's BS. It's been 10,000+miles and I still love my ninja as much as I did when I first bought her... I'm glad you're considering the 250. Starting on one of those supersport 6's could get u in alot of trouble. You'll really enjoy this bike...
Positives:
70mpg
very cheap insurance
110mph+ top speeds(not bad for only 250cc)
excellent brakes for a 2fity
looks better than the ex-500...sportier. Some even think it looks like a 6
great bike to learn on.
more than enough power for the street.
low maintenance : tires last 8000+miles(although the edges of my front tire went bald at 4000miles- very hard cornering)
light weight: easy to toss around in the tight corners.
Negatives:
Don't plan on riding with any of your 600+ riding buddies, u'll have alot of trouble keeping up.
In the twisties u have a chance, but even there a good/decent rider should have no trouble pulling away: they have better ground clearance, suspension, bigger/grippier tires....etc
In my opinion the positives definitely outweigh the negatives, especially if your riding with great guys like steve who adjust their pace according to your riding abilities/bike...
Look through cycle trader magazine: I've seen a bunch of used Ninja 250's in your price range.
Go to
www.ninja250.net for more info... It's a discussion board much like this one, but dedicated to the ninja 250. Not many from the bayarea although they're very friendly and could give u a price range depending on what year/condition 250 your looking for.... good luck