According to my med school advisors...
If you are at a US allopathic school and did well on Step 1, you don't need to take Step 2 before the match. You need to pass Step 2 before beginning residency, so taking it any later than April would be risky.
If you have a low/average Step 1 score, it might be to your advantage to take Step 2 now so programs can see your score before offering you an interview and/or ranking you.
From looking at residency websites, it has been my impression that most programs will not offer FMGs interviews without their having passed Step 2.