On a past trip to Prague, my husband and I walked here from the St. Wenseclas Statue (Muzeum metro stop), only took 2 minutes. It's on the same big street, located inside a shopping corridor on the left side of street if facing the statue.
The space is large and has nice decoration of tall bamboo trunks, and there is a bar. Seemed very much like a tourist restaurant. The menu is not vegetarian but has a few pages devoted to vegetarian dishes (using faux meats). Vegans beware - just about everything contained dairy.
If you choose to eat here, I recommend that you ask the kitchen to use separate cookware or at least rinse the ware when making your vegetarian dish.
Otherwise, it's only a short walk to Radost FX vegetarian restaurant (past the statue to the right), or walk towards the Astronomical Clock/Old Squre and you will find Country Life veggie buffet.