The bus would be from Capo to JFC, not Lago. Sorry.
As to the difference between the Montessori and International School - I think it depends on the way your kids learn. Both are good schools, so a visit would be advised. Not sure about admittance to the International School - think some grades are at capacity and waitlisted. May need to inquire.
I do know that the International school is slightly more expensive and does not offer the before and after school care that Montessori does (for a fee, of course).
Sorry I couldn't be more helpful!