I would buy a ZED fare ticket for at least the return trip, then try to get the J/S. Also, show up USA outbound at least 60 mins prior for passport check. (check validity vs. expiry date). Upon return to USA I would show at the ticket counter AT LEAST 2 hours prior, as there is usually a massive line at the ticket counter/passport check/ security. If you cant get the JS, you use the ZED ticket. The ZED ticket IS refundable as I've done it before. We just flew GRU-DTW last night, and there was about 50 people in the ticket counter line, 150 people at security and about 200 plus people at passport check. It would take at least an hour and a half to get through that line. FWIW. Enjoy your trip, LA is great!