Hey adriana, jer here.
First and foremost, congrats on your impending move to Sunny Spain

! A dream come true for most.
Ok, your question is a bit broad but I can tell you how I feel as an American here in Madrid. I feel that I am treated as nicely as I can be here, I really never feel like a foreigner.
I am also a bit of an exception since my lifelong passion for this country has lead me to learn a LOT about it in many aspects of the country, so people (Spaniards) see that in me (it's like an aura) and appreciate it. I also do not look American but rather Italian or Greek, I have rather dark skin and hair so I kind of blend in

.
My advice ot you is that you try to truly "Live Spain" during your time here. Many foreigners come here as ex-pats and (no offense to the English but they tend to do this a lot) look to only get together with people from their home countries instead of opening up and branching out in the Spanish society. For example, there is an Amercan's Club here in Madrid as well as a British Ladies Organization and many other British social clubs. Ok, I am not saying that you should lose touch with your identity as an "Americana" but just do not stay in that limited little "world within a world" while over here.
"En fin", Spain is an AMAZING country and has much to offer in it's culture, history, society, etc... so get to know it. You will be more fulfilled if you do so and the "locals" will notice that in you and respect you more than if you simply remain "100% American". I hope you understand what I mean, it is a difficult concept to expalin sometimes.
Enjoy Spain and don't hesitate to look me up when you are here.
Saludos,
jer...