Hey, Medic 101.
US training hospitals will not allow an observership or other clinical rotation until you have successfully completed at least one of the USMLE Steps. Additionally, I have not found any that will allow a foreign student to complete an observership/rotation until you are in your final year of medical school. (That is to say, you have completed the year previous to your final year... so the summer before your final year you would be good to go.)
To make things even tougher, unfortunately, an increasing number of programs will only allow foreign students who are studying at medical schools that have an existing academic relationship with the hospital. I ran into this at three programs where the director was willing to allow me to come, but the hospital/university denied it because my school did not have an official relationship with theirs.
With that in mind, I would suggest that next summer does not look good for an FMG-student in the second year of medical school. Now, if you know some US docs, you might be able to set up something like an unofficial observership with an individual or private physician before your final year (which is what I did), but an official observership or rotation will not likely be in the offing at this point.
"When I haven't any blue... I use red."
- Pablo Picasso