Hi there! As a fellow restaurant/catering guild (Om Nom Noodles is a Pandaren noodle shop), I welcome you to the neighborhood! 
You’ll find MG’s Alliance side has a ton of active vendor RP. As was suggested, I recommend you check out the many regular RP Market events held here.
The Stormwind Weekly Market happens on Monday nights in Stormwind. This one is very active with vendors, entertainers, and RP shoppers. It takes place in the Harbor Overlook.
The Duskrose Wandering Market is a travelling market that tours all of Azeroth with themed markets that match the setting of the month (that one is every other month).
The Shadow Sands Bazaar is a morally grey market event in Uldum (also every other month). They sell some shadier goods, but regular items, too.
And the Occult Faire happens a bit more sporadically in Raven Hill, Darkshire, but it’s always tons of fun. Potions, fortune telling, spooky goods, and also food as well.
Also, be sure to keep an eye on this forum as most big RP events (such as festivals, food faires, etc.) looking to collab with vendor RPers will post here. As for a physical shop location, as mentioned above the Mage Quarter and Cathedral Square are the more popular RP spots in Stormwind. For those, it may benefit you to check out the many shops in those areas to find one that fits your shop style.
Since vendor RP here is so popular these days, you might find it tricky to get a spot that is always vacant. However, most guilds don’t use those spots all the time, and you can always work out a ‘time share’ sort of setup with other GMs (example…Om Nom uses the ‘Essential Components’ shop in central Mage Quarter, but only on Wednesdays.)
Again, welcome. And if you need any other help getting situated, just ask. 