So the simple answer is the same as in any other Western country — as in any big city, just go to a club that looks the other way and ask around. Google Gay Parade conventions or schedules (city name) and you will find the time when most gay people travel around the city.
A travel agent can help, not all hotels are explicitly alternative lifestyles, and instead have been»adopted»by society because of their acceptance or simply because they have a critical mass of gay people staying at certain times (like during conventions, which is why I created you). Cities such as Puerto Vallarta, Cancun, Mexico city, Acapulco, Guadalajara, and Cape San Lucas have thriving gay communities. When you get there, ask the hotel staff about the local gay clubs, and staged gay clubs in some cities have special sightseeing offers, magazines, brochures with LGBTQ-friendly businesses that may not be (or may be, depending on the location), but can be provided on request.