First of all, your snaps are very impressive Keep posting
I thought to use the flash but again...the subject was behind the glass and it was possible to have flash reflection from glass. I couldn't keep my lense directly on the glass as well as there was an obsticle between me and the glass.
This photo can tell you what I mean
A polarizer can help on the reflections you have showing in that shot. Although, a polarizer will not help with flash reflection. It is still a great shot.