It is legal to ride two abreast here in Arizona - as long as it is practicable. Just as you are supposed to ride to the farthest right side as long as it is practicable (Practicable means basically safe for you on your bike)

Anyway, you need to use your common sense - If it is too narrow to ride two abreast, don't. If it is too narrow to ride one abreast - do it anyway! Hopefully, they will build you a bike lane it the next millenium!