At least for me, I felt pretty cool (relatively speaking) so long as I was in the shade and had proper ventilation. For your situation, I'd get a reflective tarp instead of dealing with foil, and if you're using foil, my intuition is that you'd want it on the outside of the window, because being on the inside causes the glass to absorb some of the heat going through it twice, and the foil conducts heat, which will contribute to heating the interior. It'd be better to have the foil suspended away from your window so that it can't conduct heat it manages to absorb at all.
Your swamp cooler? Your airflow will be terrible with a filter, and I can't imagine you'll have enough power + water to keep that thing going like you'd want. Plus, for me, I absolutely hate humidity in conjunction with heat. The playa is just awesome with respect to the concept of "dry heat". I remember waiting in line to leave the playa and just having the door open to the van meant we stayed cool. So for me, I'd ditch the swamp cooler altogether and use the space for something else.
Just my own two cents.
"The essence of tyranny is not iron law. It is capricious law." -- Christopher Hitchens
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