No ideas here, but I want to keep you question alive. I'll be going to
MNSSHP later this month.
These will be mostly night shots, so would everyone recommend that I get my external flash before this trip - sorry if this is an "obvious" question; don't know if (a) the built in Rebel flash is "good enough" for outdoor night shots (haven't tried it yet) or (b) if it is worth "lugging" around the extra flash.