If you have a cel phone (and I believe I'm the only person left in the USA that doesn't), check to see if they do dial up service thru your cel phone. Got a buddy that does that, and while it does chew up his minutes if he uses it before his nighttime minutes kick in, it does connect up fairly easily (hooks up via cable to his usb port), and gives him ~2-3 times dial up speed.
Other than that, I believe Earthlink gives 30 days free, and probably has some of the highest reliability, imho, of any of the dial ups left out there.
Oh yeah, and enjoy your vacation!