I suggest you make that "near future" a year from now. Stick it out. $15,000 is well worth a lawsuit. Wouldn't make no mind to your employer to sue you but would throw you into a tailspin trying to defend it while on probation at a new job. Check the reimbursement plan carefully. If it has an attorney fee provision you could end up paying for your employer's attorney as well as your own.
Or, just write a check to your employer for $15,000 on the day you resign.

