I think Flushing is a given. I'd also vote for:
74th St./Roosevelt-- it's a 5-min walk to Ayada Thai on Woodside Ave (still my local favorite); or get some papri chaat at Rajbhog Sweets on 37th Ave--my fave snack in the 'hood. And pick up some pan de bono (Colombian cheese bread) at La Abundancia before you get back on the train.
And then: While I'm a huge fan of Elmhurst, all of my favorite places are around Broadway, so a bit of a walk from Roosevelt. I'd say either hop off early at Hunters Point for pickled pork tongue and a few other apps at M. Wells (assuming you can get in quickly)...or get off at 103rd/Corona Plaza for some old-school Queens: an Italian sandwich at Leo's Latticini/Mama's and lemon ice at Lemon Ice King.
OR get something off of Junction Blvd--don't know that area too well, but do like Rincon Criollo for Cuban.
And you might want to walk a stop, like between 74th and 82nd, or 82nd and 90th, so you can try a taco/quesadilla or Ecuadorian truck.
Clearly, you'll have to make the trip more than once!
72-27 37th Ave, Queens, NY 11372
40-09 Junction Blvd, Queens, NY 11368
46-02 104th St, Queens, NY 11368
Lemon Ice King of Corona
52-02 108th St, Queens, NY 11368
77-08 Woodside Ave, Queens, NY 11373
63-10 Broadway, Queens, NY 11377
M. Wells Diner
21-17 49th Ave, Queens, NY 11101