Do you have a car? If so, find the nearest hotel and park in the lot, close to the building but away from security cameras. Open up your laptop. If you get a connection, go for it. If not, move on to the next one.
My friend works at the Standard in Los Angeles. Frequently when I'm there during the summer I spend my day chilling out there by the pool and doing IM. It's very nice and luxurious, and you get to meet interesting people.