I picked girls just because a majority of my dreamies are girls, but I do like to have a few boys in my town. I have 3 on my main and will have 3-4 on my second town.
Ik it would be hard to complete your town w/ only one gender. They need to mix personalities between genders in the next game. I don't see whats wrong w/ females being jocks and males being normal.
Assuming I could keep my regular town, I would make a town of all smugs. Everyone would be hitting on each other and acting geeky together. It would be insane. xD