Switching groups/locations after SA

I am going to be interning this summer at an EB (EVR/LAZ/Centerview). I would like to switch from CHI/SF to NY after the summer. The group I'm currently in is a more focused group than its counterpart in NY (i.e. niche Tech group compared to generic Tech group). The two groups do work together at times, but the CHI/SF group often keeps to its focus. I'm completely fine switching groups altogether as well- location is most important.

What is the best route to accomplish this transfer? When I interviewed for the position, they asked me specifically if I am interested in the city and while I was at the time, my view/life situation has changed. Should I start making NY connections before/during the internship? Would asking HR be a bad move (no leverage and could get the offer revoked)? Should I wait until I (fingers crossed) get the return offer or maybe make it known earlier on? 

Appreciate any insight people have.