I was just advising a client about when he should take his Step 2. The answer to this question is different depending on a medical students' step 1 scores, how competitive her/his specialty choice is, etc. I can make one suggestion to everyone, though:
On the ERAS form you can check a box to ensure that your Step 2 scores are not automatically released to residency programs. I recommend this. If your score is poor, you can hold it from programs to which you are applying indefinitely. If it is good, you can choose then to release it with very little delay. This move keeps your options open.
Contact me for a strategy session now - before the application season starts. I can assist with decisions about rotation scheduling, the need for research, letters of recommendation, etc.