I love to bike ride on the weekends in the Texas Hill Country. I like to get in between 25-50 miles on Saturdays and Sundays. Varied routes is preferable, it breaks up the monotony, plus if you are riding alone, you do not want your routine to be predictable. Always make sure someone knows where you are riding, take your cell phone (but don't talk or text while riding), water on your bike, a couple of emergency dollars if you have to stop for a drink (I can't carry enough on my bike with 2 bottle holders), and some pepper spray for dogs and/or unwanted human interaction.
I would say NO WAY to listening to music with headphones! You need to be able to hear traffic approaching you from behind.