This reply should be pretty simple for you, depending on your situation. Whether you are flexible or not, in regards to travel, and even relocation, it's essential, to be honest in your answer. If you are unsure, it's okay to let the interviewer know that you are open to ideas in the future.
"Relocation is something that I would consider in the future, depending on the circumstances and the opportunity. As far as travel goes, I am open to some overnight travel as required."
"At this point in my life I am not interested in relocating, but things can certainly change. Could you share with me the travel requirements in this position?"
"I recently relocated to this city so, moving again I hope is not in my near future. As far as travel goes, I am very open to overnight travel. I realize that you have a few locations in this state so if you need a manager who goes between locations, I can certainly accommodate."
"Much of what I do in the digital marketing realm can be done from anywhere in the world. I can travel to accommodate any of your needs in this role. For relocation, that is not in my plan, but I am open to discussions."
"Your company has many locations, and I am open to working in a variety of them. With that said, overnight travel is difficult at this time with my school schedule."
"As a business development professional, I am no stranger to overnight travel. Currently, I travel about ten nights per month. Do you have a travel schedule in mind for this role? As far as relocation goes, nothing is off the table at this time."
"At this point in our lives, our family would be unable to relocate. However, I am very open to travel to conferences, teacher training opportunities, and more."