Happykid is a native Spanish speaker too. She took two years of Latin in high school in addition to attending weekend Spanish school for her reading and writing skills. The advice she was given was to go straight to AP Spanish. She didn’t end up doing that because she wasn’t applying to colleges that needed more than two years of foreign language.
Dead languages are fine for college admission. Don’t worry about that. It is fine to stick with Latin if you want to. You already speak Spanish as an additional modern language. Since you can read and write Spanish reasonably well, you could be looking for an online AP Spanish Language or AP Spanish Literature course specifically designed for heritage speakers. The school district I live in does offer those sections. Heritage speakers still need fine-tuning of their language skills just like native English speakers need to take English language arts and English literature classes.
If you’d like to take some Spanish lit classes once you get to college, it can be worth your time to prep a bit and take the Spanish SAT II exam and/or the Spanish CLEP exam. Those scores will sometimes place you out of foreign language requirements altogether (Happykid got 12 semester credits for her CLEP score) and often will get you placed into an upper-level course.