(Today I'm taking a cue from my friend, who in the blogging world goes by Sera. I adore her, and when I saw her letter posted on her blog I melted. So, here is my shot at at it)
Defend your sisters till the end. They will still be your best friends in 14 years, and I'm guessing 14 more after that, and 14 more after that, and so on.

When your living very far from home, completely broke, about to sleep on a disgusting airport floor and your best friend is mean to you just break down and cry. It won't change the situation at all, but you'll never feel more love for your parents as you do when they're sitting on the end of a computer listening to you bawl your eyes out thousands of miles away. However, no matter how serious you maybe about changing your flight and heading home that very day-don't do it!!!! That next week you spend in yet another country will be one of the greatest of your life. And, you'll be home before you know it.
Yes, another country. You know what-for a little while you'll have the opportunity to call a city and country that you've always dreamed of visiting "home" Take it all in, enjoy the mundane and write to your family often.
His name is Jose. I know this doesn't make sense right now, but know this, and don't forget it. Really.
Now, that your back... yes I was very serious about the "right now". The fact that you can do that right now is the beautiful part.
You probably don't want to hear this but mom and dad usually know what they're talking about.
Jump in the fountain. You wont get deported :)