Hi Krista,
In the US, this is perfectly allowable! I normally dance as a follower (as I am a woman). However, where I live it is often difficult to find partners especially once you hit the silver level and on up. Last year, I danced several competitions as a leader as I had a friend who could follow (who was also female). We didn't win anything; however, we did make callbacks in our dances and I have often seen that the same-sex couples tend to do better as in order to be able to dance both the leader and follower parts, one must develop a better sense of the moves, the dance and the connection. I would say if you are interested in doing this, by all means, full speed ahead!!

Best of luck to you!