Inexpensive good place to eat near Union Square?
Thai noodles perhaps? There's a King of Thai located not far away from Union Square.
There's been several threads on this subject. Do a search, and you might find postings on places like Shalimar or Sears Fine Foods or Dottie's True Blue Cafe. Or about Vietnamese places in the Tenderloin. My only caution is that the Tenderloin isn't the most family-oriented place in the city, and can get a little dicey.
If you're willing to go a little further, I'd recommend Destino, for Peruvian-Californian tapas, which will be great for sharing among big groups. It's on Market Street between Valencia and Guerrero.
There's a current thread mentioning Plouf, a French place for mussels (the other stuff was OK) in Belden Lane, a little alley with a bunch of European restaurants. B-44, a Catalan place is right there, and I also enjoyed their tapas. Paella type rice dishes there are also good there.
Some decent places include:
*Ar Roi on Post (good Thai food, clean place; waitress might sneer if you don't order a lot, LOL)
*Max's on the Square on Geary (part of the Max's chain)
*Cafe Claude on Claude Ln off Bush (casual French, authentic French cafe atmosphere, outdoor seating)
* various Japanese restaurants on Geary and O'Farrell within a few blocks of Union Square
These are all in pretty safe areas of Union Square/Tenderloin.
It will be tough to seat a dozen people together, though, in most places, unless you go during off-peak periods.