Suggest you go to
www.ncaa.org, Eligibility Rules.
Here's a link that may help as well:
http://www1.ncaa.org/membership/enforcement/amateurism/player_contacts/mlb_info/mlb_faq?ObjectID=25543&ViewMode=0&PreviewState=05.As an enrolled student-athlete can I tryout for a professional team without jeopardizing my eligibility? As a prospective student-athlete?
Tryout Before Enrollment: A student-athlete remains eligible in a sport even though, prior to enrollment in a collegiate institution, the student-athlete may have tried out with a professional athletics team in a sport or received not more than one expense-paid visit from each professional team (or a combine including that team), provided such a visit did not exceed 48 hours and any payment or compensation in connection with the visit was not in excess of actual and necessary expenses. A self-financed tryout maybe for any length of time.
Tryout After Enrollment: A student-athlete shall not tryout with a professional athletics team in a sport or permit a professional athletics team to conduct medical examinations during any part of the academic year while enrolled in a collegiate institution as a regular student in at least a minimum full-time academic load, unless the student-athlete has exhausted eligibility in that sport. The student-athlete may tryout with a professional organization in a sport during the summer or during the academic year while not a full-time student, provided the student-athlete does not receive any form of expenses or other compensation from the professional organization.