Hello! I’m a current Caltech undergraduate, so I’ll do my best to address your different questions.
For your ACT score, GPA, and class rank, I think it would be possible for you to be admitted. According to another site (http://www.prepscholar.com/act/s/colleges/Caltech-ACT-scores-GPA), Caltech’s average ACT is 34, with the 25th percentile being a 33. In other words, about ~25% of Caltech students would have an ACT score of 33 or lower.
If you do decide to add another AP class, adding an AP class in a science subject could boost your chances at getting into Caltech (assuming that there exists at least one such class that you have not taken yet). But even taking an AP class in a non-science subject could be useful - I think the admissions committee does like seeing students that are “well-rounded.”
Yeah, Caltech doesn’t prioritize athletes. Athletes are offered the same scholarly opportunities (tutoring, etc.) as all other students. I do have a number of friends on various Caltech sports teams (including the soccer team) - they primarily play because they enjoy the sport.
Caltech Admissions is blind to race, gender, ethnicity, etc. - they make admissions decisions without considering those pieces of information. Once you get in, there are various opportunities available (for example, you could join CLASES, the Latino club on campus), but that will not affect your admission chances.
I would say that having good admissions essays could really help your chances at admission. What are you interested in? Is there anything that you are super passionate about? If you do choose to go to med school, what would you ultimately want to end up doing (what specialty/age group/etc.)? Ultimately, you want to have your essays (especially your main essay) tell a story. If you can convince them that you’re really interested in STEM, then the lack of STEM extracurriculars will not hurt you as much.
Also, it’s never too late to start adding some STEM extracurriculars. Maybe get into contact with a doctor and do some shadowing. Or maybe contact a professor from a local college and start doing research-related activities in that lab. You could discuss it in your essays, and you could continue such activities throughout the school year.
Finally, I would like to briefly discuss the implications if you do decide to go to med school. Caltech does have a number of students each year that apply to med school; however, if you are 100% set on going to med school, Caltech might not be the best place to go. For one, I have the impression that med schools care a lot about one’s college GPA and thus might choose a 3.9 student from a state school over a 3.4 student from Caltech. Secondly, I get the impression that med schools look for students with lots of extracurriculars; Caltech students can have time for extracurriculars, but likely not as much as students from many other colleges.
Regarding the various fields at Caltech, I expect that most of the undergraduates who end up going to med school get their degree in either biology or chemistry. Another potentially related department that could be interesting to look into would be the computation and neural systems program, which, among other things, is involved in a lot of the brain research on campus.
Here are links to these departments (hopefully they still work on non-Caltech internet systems):
Biology and Biological Engineering: https://www.bbe.caltech.edu/
Chemistry and Chemical Engineering: http://www.cce.caltech.edu/content/chemistry-caltech
Computational and Neural Systems: http://www.cns.caltech.edu/
Best of luck, and feel free to send me a message if you have any more questions that I can answer.