Very interesting thread - sorry it's taken me a while to find it!
I guess one thing I'd mention is that most male-to-female transgender people would really not want to be referred to as "men" - that would be particularly offensive to mtf transsexuals, for example. Many cross-dressers would prefer to be referred to as women rather than men too. So I'd be careful to make a distinction between male and trans clients - e.g. say "we welcome male, female and transgender clients" - or "we welcome clients of all genders and sexualities" (the latter will also imply that you are lesbian, gay and bisexual friendly too) - or perhaps "We are lesbian, gay, bisexual and transgender friendly".
Generally, it would be cross-dressers who would be most secretive - many cross-dressers are not "out" at work or to their (non-cross-dresser) friends or even their partner.
Whereas transgender people and transsexuals living full-time as the opposite gender to which they were born would either be "out" to everyone, or living in "stealth" - i.e. to all intents and purposes a member of the gender they are now living as - depending on where they are in their transition.