Localita and the Badasserie would be a great breakfast or lunch option (or both, it's that good!) It's all vegan and lots of different options such as bowls, breakfast sandwiches, smoothies etc. Its walkable from where you will be and they also deliver! http://localiyours.com/localita/
Mendocino Farms is a good spot, they usually have a lot of prepared stuff that is vegan. There is also a Whole Foods on 8th and Grand with decent vegan options for prepared stuff, salad bar etc. They have a coffee bar as well and usually a few vegan pastry options.
Bar Ama has yummy vegan options, including a queso dip! http://bar-ama.com/home.html
Definitely check out Ramen hood, also at Grand Central Market, G&B coffee is excellent and Golden Road has vegan pierogi.