If you decide to use a character boost to get to level 30 so that you can jump straight into New York, you'll be missing out on a fair bit of content from DC (side missions, progressing through World Tiers, and I believe even some achievements/in-game commendations won't be attainable).
If none of that matters to you, then have at it. Otherwise, best to play the game in order (get to level 30 by playing in DC, then travel to NY when you're ready.)