Stefani, why can't you use a normal window unit?
I've seen the portable ones in use at parties- I think they're more expensive than the same BTU of a regular AC unit, but a good value if you'll need to move it around a lot.
We have central AC, however DH likes to save $$$ and keep raising the thermostat to 80 or so!
Keep a big bottle of ice-water on your desk:)