Cancun is divided into two distinct areas: the upscale grand hotels along the beach for foreign tourists, and the working class downtown Centro district, (2 miles from the beach – final 15 photos below) where the hotel workers live and shop (at Sears and Wal-Mart, etc.).

In the Centro are Cancun’s three gay bars (and possibly a mixed bar that sported a ‘bi’ night).
Gay life is quiet and subdued in Cancun (except for the loud dance music in the three disco-bars).

There is an annual ‘Gay Festival’ that is touted as a big event by the promoters but it is hardly city-wide and is usually confined to the one or two hotels booked by the organizers. See Passport Magazine story about the beachfront hotels and gay life.
Read the story about gay Mexico