It is perfectly acceptable to ask how much travel is involved. That way, you can weigh how much you would need to be on the road and make an educated decision as to whether the amount of travel required fits in with your lifestyle.
What's most important is to get a good understanding of what's involved before you are offered the job, rather than being (unpleasantly) surprised after you have already been hired.
More Job Interview Questions and Answers
Interview Questions and Answers
Typical job interview questions and sample answers.
Interview Questions to Ask
Questions for candidates for employment to ask the interviewer.