A couple of times, I've read posts insinuating that some of the women in Brazil that are interested in men may have had a sex change operation.
Although my personal experience is limited and I have asked a few people here, this is not something that is common or something that I had found anyone had ever heard of happening to someone personally.
I'd hate to see some sort of Urban Legend start because of a couple of posts.
Because of the diversity of people involved in this process, I'd say your chances are the same or slightly less than in the US of meeting someone who has changed gender. That is to say, if you solicit prostitutes in the US or go to transgender bars your chances would be a LOT higher than the typical guy going on a date.
However, if anyone has a personal story. It might help to clear the air to post it.
Anyway, it just seems bizarre to me to see people put this out as a serious concern (for the man looking for a serious relationship, NOT for the man on a sex tour). I would really hate for someone to be put off because of concerns in this area.