I would pick Madrid for the fun and entertainment factor, the weekend sightseeing to other pueblos factor, and the ease of understanding the language better factor.

IN Valencia and other places in the north, there may be a dialect factor to consider, regions speaking their local language (Valenciano, Catalan, Basque) and then in the south (Granada) the Andaluz accent can be unforgiving on the ear.

I absolutely love all the choices above, but as far as studying the Spanish language, I would opt for the central part of the country. Madrid being the best place to explore many places.

I agree with Laduque that Madrid is may be the best place to learn Spanish, for many reasons.

I love Madrid, but remember that "tflanag1" are planing a summer course. May be for them the beach is important.

I don't think the accent is decisive, like English, Spanish has many different accents, not only in Spain but in America. Traditionaly the accent from Burgos was considered the best one, but now all of them are acceptable. Furthermore, biligualism is a real fact of Spanish society that I consider very interesting.

However, Madrid is a great choice.

I wasn't dissing the accent thing, I was just suggesting that the Castellano accent in Madrid is more "international" (if you will) and may be possibly easier to pick up on.
I don't think there is a "best" accent in any language.

Also, Madrid is central to the whole country so even the beach (Valencian coast) is a mere 4-5 hours in car. Being a foreigner in Spain, I would want to experience the culture, the small towns, the art, food, and every other aspect of a foreign country.,

I'd also recommend Madrid, unless it will be in August. The city is practically empty then. I like Madrid because you get a little bit of everything. Small town feel in parts, and big city feel in others. Along with that, travel is SO easy, being in the center of the country. Beach is close, many of the famous small towns to visit are close (Toledo, Salamanca, Avila, Valle de los Caidos, etc). Also, with the speed train, you can even get to the other great towns very quickly: Barcelona, Sevilla, Granada, Cordoba, etc.

I studied in Granada during the winter and LOVED it. However, for the summer, I would recommend Bilbao! I spent the summer there for my first study abroad experience and really liked it. Its a big city, lots to do and see in the North, good climate (aka not super hot in the summer!), plus you can get to the beach on the metro in 20 minutes! Another Bilbao plus is the very low percentage of foreigners or other study abroad students. Thats not the case in Granada or Salamanca, especially in the summer months! Just a thought:-)
Kelly

OK, I'm chiming in with my vote for Salamanca. I agree with previous posters that the accent in Madrid is the most universal, but I spent a summer in Madrid studying and it was unbelievably hot. There's a reason everyone leaves in August, and the city is virtually empty. It's waaayyy tooo hot. Salamanca is a jewel of a city, it's within train distance of several amazing day trips (Segovia, Vallodid, Toledo, Portugal, even Madrid) for weekends. It's a huge university presence, so there are many students around, which I found to be a plus for the atmosphere. RE: Granada, beautiful city, but I think the Andalusian accent would not be the very best place to learn immersion spanish.

I went for a two month language program in Salamanaca and ended up leaving for Madrid after 1 month because I was bored..well, I mean, I had seen everything and wanted a change. Madrid was fun, and for me the heat was much better than the heat in Sacramento (where I am currently living, which is around 105 during the summer).