Hi everybody!
I've been together with this amazing guy for almost 6 months now and I'm really crazy about him. Next week I'm going to go to Spain with a lot of friends for 10 days. And he doesn't really like that, I mean he said I'm allowed to go and it's not that he made a problem out of it. But I notice that he's a little concerned. Because well, it's mainly going to be partying over there. And I understand he's a little bit worried but I booked this holiday a long time ago so..
And now, when it's our 6 month-anniversary I'm going to be in Spain. And so I wanted to do something nice for him on that day. My sister lives right next to him, so I was thinking that maybe she could put something on his frontdoor or in his mailbox or something. But I don't really know what? Well I was thinking about a card, but I also want to give him a liitle gift or I don't know. A sweet romantic gesture.. Any ideas?

Lots of places to look for romantic ideas:

romantic ideas - Google Search (http://www.google.com/search?q=romantic+ideas&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7)

TheRomantic.com: 1000s of Creative Romantic Ideas and Free Expert Advice on Love, Relationships, Sex, Kissing, Dating and Romance (http://www.theromantic.com/)

Romantic Ideas (http://www.romanceforeveryone.com/romantic-ideas/)

Next week I'm going to go to Spain with a lot of friends for 10 days.

What's that trip about? I assume you are 18 yr-old. I don't think there is a 10 day holiday break in Senior High or College...

Romantic ideas... hm... I ALWAYS suggest this "cook for him!":D

You could put together a "care package" type bag for your sister to drop off at his door.
Romantic Care Package Ideas (http://www.improve-your-romance.com/romantic-care-package-ideas.html)
What you put in the gift bag is entirely up to you. Something cute, something sweet, something that means something special between you two, etc.