Dang... I wish I'd known about that ISIC card about 8 years ago...
Seriously, since you're 17, a 21+ ID would have to be absolutely flawless to be believable. I would go for a 19+ ID. (A lot of the bars around Boston that aren't 21+, are 19+) That way, you can't drink, and you'll get hit with a higher cover, but you can hang out with your friends, etc. And in 2 years it will magically become a 21+ ID