I have a male and a female and they both get along great. My parent's also live out of town and traveling by car really isn't that much of a hassle except they both take up the entire back seat with their travel kennels and other items. They are not exactly "light packers"
It's certainly more work having 2--especially in the beginning with regard to housebreaking and training but I LOVE having 2 yorkies. I can honestly say that I will always have more than 1. I love them both so much