Take Ajo Road west all the way to Why, turn left (South- make sure you come to a COMPLETE stop- usually a cop at that corner) and continue as usual to the border. If you don't know how to get to Ajo Road and you're on the north side of town, take I-10 east (which is really south), go right on I-19 south toward Nogales, and the first exit is Ajo Rd. If you're on the south east end of Tucson, take I-10 west, then take I-19 south, turn west on Ajo, etc. Should be a great weekend.