Well, I suppose it all depends on what "everyone" really wants. And how much people want to acknowledge the setting. So, a generic location selected/created by the staff to suit the desire for players to do whatever they wish and be able to play whatever they want would be reasonable option.
The location should definitely be in Faerûn though. Wizards of the Coast will not (and has no desire to) offer any support for regions such as Kara-Tur, the Hordelands, etc. in the new edition.
Now, onto some actual locales!
Waterdeep: By and large everyone knows of the City of Splendors, if only by name. It's fairly tolerant of races, though people begin to get unnerved from drow and upwards. Perhaps something could be worked up with the Lords, since the presence of a Thayan enclave has been good for the economy. Perhaps a Bazaar of the Bizarre would be even more so! If they could be ensured wards are in place to keep the more...unnatural denizens out of the city.
The Muzhahajaarnadah (Dark Calimport): The dark bazaars of the Calimport underworld contain no restrictions. From demon lords to archmages of other worlds to dragons. The only problem is...it's pretty evil. Though these dark bazaars to contain powers that would keep the place from being a utterly lawless anarchy (violence gets one ejected by the Gray Callers). And so, they get poofed to the combat room!
Those are the ones I can think of off the top of my head.
Silverymoon is out of the question, its mythal would keep some patrons from entering (evil demons, devils, dragon, drow, duergar, giants, goblinoids, mindflayers, orcs, and trolls). And even if they got by the mythal, they couldn't stroll around openly.
Cormyr is a no-go, too low magic and wary of masses of foreigners.