When Charles Martin became executive director of the South Beach AIDS Project in 2005, he found that all the educational materials were in English and only showed pictures of gay white men. Since most of the agency's clients are black and Hispanic, that didn't seem very effective. He replaced the old posters with bilingual ones showing black and Hispanic male couples. Invisibility in the gay mainstream is just one of the special challenges facing gay black and Hispanic men. Those issues were front and center last weekend at Miami Beach Bruthaz, a four-day, mostly male South Beach retreat for gay blacks and Hispanics.