Flew in Vietnam recently and the flight was operated by a Lithuanian airline and crew (but booked through Vietnam Airlines) so they must be struggling.
Kata is definitely very Russian now, not necessarily a bad thing but can see how it could be overwhelming for locals when such a mass of people with a different culture arrive at once.
Mexico City is a great place to start and see what you like - lots of gay bars, opportunities etc and you could tag on Oaxaca or Zipolite for the gay scene as somewhere the throngs of tourists are not yet destroying.