We homeschool and both our dd's play travel. It depends soley on the school district whether or not you can play school ball. Some require you to take a class, even PE or Art, or some other elective course. Some do not require that you take any courses, and some are not homeschool friendly whatsoever and will not allow your child to participate in any school-related functions. You can always play in the local rec division, however, because they are community related, not school related.
A lot of kids seem to prefer travel ball over school ball, and either way you choose will get you noticed by a college recruiter if you are good.