What a wonderful dilemna you have - languages are wonderful to know and I'm impressed with your level!
Depending on your intended major or possible career, Spanish (as is your case) could be the difference in putting you over the top. If you believe that you've maxed out your interest in the subject and want to show your proficiency in a meaningful way, you might consider taking the AP exam. Students can take the exam without taking the course, and AP testing is always the first two weeks of May. Talk to your counselor about this option.
The SAT II exams for foreign languages are another option to show proficiency and are administered throughout the year (on official testing dates). Taking the SAT II would also allow you to use your scores in the college admissions process.
Another way to show language proficiency is to take the foreign language exam when you begin university. Colleges will often offer these placement / credit exams during orientation, but can sometimes be taken at other times through the department. Please note that there's a difference between placement and credit. It is becoming more frequent these days that the tests place you into the appropriate level, but sometimes once you complete the placed course (with a C or better, for example), the university will give you credit for the completed course as well as the courses that proceed it. These credits may meet requirements for general education and/or degree program plans or may simply allow you some cushion in your semester load(s) and/or elective credits.
If there are colleges that you are interested in or are considering, I would encourage you to research their admissions requirements and recommendations to educate yourself. You don't have to know exactly where you'll be applying, but the research will give you some general knowledge especially if you know the type of institution (liberal arts, research, etc.) you see yourself attending or your possible intended major.
I will also add that you may want to also do some research regarding the science courses. Before doubling up and potentially making your upperclassman years miserable or overloading yourself, I would do some research about who wants what. If you're interested in engineering, for example, schools can be very specific about what sciences they want to see. Potential science major? perhaps pre-medical? Institutions often look for well-rounded candidates rather than "pointy" ones. Pointy candidates focus too much on a specific thing and lose sight of the forest for the trees. Doing some homework in this area would be well worth your time, in my opinion.
I commend you for asking these questions now and positioning yourself to enhance your future. Good luck!