I think you may want to check with whomever has offered these passes to you before planning a trip to Australia. A buddy pass is only good for one flight segment. To travel from the DC area to SYD, you would need to get to SFO or LAX, thus requiring 4 buddy passes each for the roundtrip. 8 buddy passes at one pop is 1/3 of our annual allotment. Also, a buddy pass to SYD is NOT cheap. You may come out better purchasing a revenue ticket if you are considering going in July as it is a slow time.

As far as Mexico and the Caribbean, I'd be careful as well. UA offers only weekend service to some of these destinations so if you get stuck you are LITERALLY STUCK!

-IFLYUA