rainmaker - presumably you are considering taking USMLEs because you plan on applying to allopathic residencies as well?
If so, just make sure that you have the test completed and scored in a range you need to be competitive by August of the year you apply to residency (again, presuming your school doesn't require you to take it). Most students take the USMLE right after 2nd year - however, a little bit of clinical experience is helpful these days. Finding the time to study during 3rd year is not...
😀