I would ask just to extend the return date (they do this all the time for people that take optional extensions on other EF trips) unless you are planning to return from a different city.

I'll likely be returning from a different city. I plan to travel around for probably a couple weeks more. Would they even extend the departure date for a couple weeks if it was the same city?

Why not ask the tour company? I would think this could be possible, maybe with an added fee or two. But in the end, it is the company you are going to have to deal with, not the Fodor's gang.

Call EFTours and talk directly to them to work out the details. You can stay after. You can't pay for one-way. There is a deadline for such arrangements. And it has to be from the departure city on the Tour's itinerary. But you need to confirm/arrange all this with them.

Oops meant to say that this is the policy for high school tours; I have never looked at specifics of college tours.

They charge extra to extend a return. Since you want to return from another city, call and ask about the price without airfare. Check flights for prices as it might be cheaper to book their flights. EF is part of a bigger tour company with EF being a low budget student tour branch . They have tours/groups flying in and out of cities all over Europe.

If you haven't booked already with EF, you might want to check with some other companies also. Explorica is the other low end student tour. CHA and Passports are middle level with ACIS and NETC being the upper end. Some of them offer college breaks/tours. Contiki is another and is more of a party tour.

Also check with STATravel as student booking is their specialty. They've had offices on many campuses for years and can used to book open end or very low exchange fee tickets for students. I last used them in 2006 when my daughter was spending 6 months in Spain and didn't know what return date she would need. The fee to change the return ticket date at that time was $25.
http://www.statravel.com/