At your size, I'd not recommend a 250 at all..
Everyone told me the same thing when I got my 450.. Way too much power for someone without experience.
Well, the bike does come equipped with variable position throttle control. And I came equipped with a brain and a sense of self preservation.
I know what's too much for me, and back off when I reach that limit.
If you were 17 or 18 and never ridden, yeah, too much bike.. But.. if you ride a 450 with knowledge that it can bite hard, and ruin your summer, it's no more powerful than a 85.
If you do get a 250 now, you'll be looking to sell it in a couple of months. It just won't have the power you need to ride..