There are a few other subtle differences between the 24 and the 66 from looking at the Raleigh website - the 66 gets a Shimano 105 rear derailleur, for instance. For what you'd be using it for, though, I'd probably opt for getting the Route 24 to save some money. The differences in equipment probably wouldn't make much of a difference in function for commuting/riding around campus sort of stuff. I would say ride both - if you like how the 66 rides better, get it!
Like SpaceNerd said, be careful and lock it well. That's why I always rode used bikes in college. (I still only ride used bikes today, but that's beside the point.)
I've never been to BikeTek's Monroeville location but I live about a half mile from their Squirrel Hill shop. The few times I've been in there I've had a mixed experience. They definitely seem to know their stuff, but the times I've talked to them they seemed to cater much more to the high end roadie and MTB crowds. I usually go somewhere else when I need to go to a shop, but there are also much worse places out there. (Your mileage may vary, of course!)
Good luck with whichever you choose...