Could I learn to speak Spanish?

Yes, definitely! Take classes in college, and study abroad in a Spanish-speaking country. Within two days of studying abroad in Spain I noticed both my speaking and comprehension improve. It helps tremendously to be completely immersed, speaking and hearing 100% Spanish, and going to a Spanish-speaking country is really the only way to do that. But definitely learn a bunch first.

Also, I’ve heard that Rosetta Stone is really good, although I’ve never used it.

Absolutely. Take classes, study abroad, and do everything else that @sliceswiththings said.

Growing older doesn’t make learning new languages impossible, just slightly more difficult, but it’s nothing that can’t be conquered by force of will and hard work!

That said, do invest in some good, reputable educational software, It is usually more helpful than books, and be sure to read as much Spanish vernacular as possible. It will give you a different spin on the language which is much more versatile and useful than just taking classes.

It really all depends on how much you really want to learn it and how much exposure you have to it daily. Once you start to learn it in school, practice by watching spanish novelas to get use to the different dialects and speed that people speak. If you grow interested in the novelas (spanish soaps) you will pick it up faster so you have a better grasp of the story lines and characters.
My husband learn fluent english in two years when he came here, simply by watching a lot of tv. Of course he had english in school but he had a better grasp because he was so into TV. Of course he was 12 at the time and younger people pick it up faster.

Yes, anyone can learn to speak Spanish. It sounds like you will have plenty of time (12 years) to learn the language, so as long you are willing to put forth the effort, you will be able to learn Spanish before you are 30.

Ofcourse! I agree with @sliceswiththings. Take courses and study abroad. I am currently minoring in Spanish and am in my junior year of college. I am also preparing to study abroad in Spain this upcoming summer. The key to learning the language is immersing yourself in it as much as you can. Take any opportunity you can to practice. My school’s Spanish department offers opportunities to practice every week by inviting students to a coffee shop on campus in order to mingle and practice with other Spanish speakers. You should definitely check to see if your school offers this as well.
ALSO, there’s free podcasts on itunes to help you practice as well!

Spanishdict.com

The best way to learn Spanish is to take a couple college classes and then travel to a foreign country and just speak it. It is a little bit like learning how to swim by diving headfirst into a pool, but I’ve found it to be the most only truly effective way to learn it.

It’s definitely possible. While I’m not yet fluent, I’ve been studying Spanish for about six years and it’s just a great language. :) It just takes a lot of practice, and you definitely need to speak it with someone, not just a Rosetta Stone type program. But having the motivation to do it and immersing yourself as others have mentioned should definitely accelerate things for you. Good luck in learning, I hope you find it interesting!