Now this is a situation I can relate to!!!!!
I am currently studying abroad in Spain, (Bilbao, Universidad de Deusto). I got here in the first week of May, and will return to the states mid august. This has been the best experience of my entire life, I am already trying to plan to go back and study at La Universidad de Deusto again for either a semester, or entire year
I love it here, and I am sure your experience will be equally great
So what sorts of things should you be ready for? I really did not experience any MAJOR shocks adjusting to life here, maybe I owe that to the wonderful advice and help I got from this message board before leaving for this adventure! There were a few little things I had to adjust to, but now these things dont bother me, and there are many aspects of spanish culture that I will miss when I leave for the USA in August (ex- concept of time...it is 4am here right now and I just have not felt like going to bed yet and with no class tomm, why not stay up all night? hehe).
Anyways, realize before you go that the first week or two will probably be a little "rough".
Some things I was worried about before I left...
-Food- spanish food is awesome!! Although there are some things that I can do without (por ejemplo- sardines baby eels!!) But there are many other foods that I love (magdalenas, tortialla espaņola, natillas, the wine, the list is endless). Try everything!!!
-The Language- I was very worried that my 6 years of Spanish would fail me the minute I set foot on spanish soil
However, I have had no problems here, in general, everybody was very patient, and after about a month, my fluency had increased enough that I had no problems in this area. Realize that you are going to make mistakes, just laugh them off and learn from them. You will be amazed at how fluent you will become when you have no choice but to use the lanugage!
-Standing out- I really wanted to blend in with local culture. I am kinda lucky on this one (I have dark brown eyes, dark hair and skin- and felt I blended in more in Spain than in the USA hehe). So I really did not have major problems here. I would suggest buying clothes, especially shoes once you get there, you will feel more like a local, and hey, shopping is FUN!!! Try Zara, Mango, Truco, and el corte ingles! Also realize though that no matter what you do, you will always stand out a little, and that is cool, be proud of who you are and where you are from!
-I also really wanted to immerse myself in the culture and avoid hanging out with other americans. This is one reason I would really suggest living with a host family. This is also where your spanish skills really increase!! Dont cling to other foreigners, try making spanish friends, you will be glad you did! People are really friedly if you just make the effort. It is great because they know the local culture...it is so much fun going out with them on the weekends because they know where the "local" secrets are!
It will take a little time to adjust to La vida espaņola, but once you figure out what is what you will find that you become very immersed in the culture and can really begin to feel like a "local". I would suggest living with a host family, that is what I am doing, and I can't say enough wonderful things about them!! Good Luck, and enoy every minute of your time there