A city a hundred miles or more from your hometown. Actually, you can do this any day of the year. Just go where people don't know you. Even if they recognize that you are a crossdresser, they don't know you and you don't know them.
For the few who were confused by my example of the expensive breast forms, wig, butt, etc. My point is, if you do a good job of presenting as a woman, as most of us would want to do, people will know that you don't just dress for Halloween. They will know that you have done this many times before.
If you don't care, that's fine. If you are out to the public already or live full time as a woman, that's fine also. I am just trying to make a point for those who wish to keep their little "hobby" a secret from friends, family and co workers.