Recommendations for a city week?

I would love to spend extended time in Seville so I would go there!

Not Marbella - too resort-y, not enough history or local culture.
I have not been to Alicante so can't speak to it.
Malaga will have good transit connections and has plenty to see but...

I think Seville and Granada are the most interesting. You've been to both - I'd pick the one you liked better and dig in to it.

Is this a course anyone can sign up for or is it specific to your university/workplace? I'd be interested in doing such a course someday!

I spent a few days in Malaga and in Valencia last year. There's about as much to see and do in one as the other. Malaga's a pleasant town with a few small museums and some interesting Roman ruins. I wasn't very taken by Granada, and I haven't been to Alicante. Sevilla would be my hands-down choice. Lots to see and do, and the best tapas in Spain, hence in the world.

Craig, just throwing this out there, but have you thought of maybe going north.
October is a good time to visit La Rioja. There is a Spanish school here. It is just around the corner from calle Laurel, which is also a pretty nice place for tapas.

Thanks everyone for your input. Prior to posting I was leaning towards Sevilla but didn't want to "tip my hand". If the course offerings in Sevilla fit my needs then I'll be moving forward with booking a trip.
@dlindstrom - While Spain has over a 100+ Spainsh Language schools, I am attempting to take advantage of a promotion with Enforex offered only in Alicante, Malaga, Marbella, Sevilla, Granada and Valencia, but thanks for mentioning La Rioja in the Fall.

If you can add time, think about spending a couple nights in Cordoba - my favorite Spanish city.