What an amazing piece of public art the Corpus Clock is. With its eerie sound, unexpected features (the creature on the top blinks), and sheer cleverness, it is almost worth visiting Cambridge just to see it. Here it is, unusually without tourists in front of it:
I emailed Gray Line Mexico today, a Saturday, to confirm that I arrive tomorrow evening and will be taking one of their vehicles into my hotel in the middle of Mexico City. They replied right away with all the information I need. I'd booked the trip through Expedia so I was half expecting a "we have not got the fax yet" reply, but instead it all worked seamlessly. Nice customer service.
When at PHL, I find that it's better to simply walk from the Rental Car return area to the terminals. The buses weave a circuitous route around the airport to reach the terminals, which are actually in close (5 minute) walking distance from the Rental Car return area. So next time, simply walk :-)