The 3.35 is fine. Especially considering your difficult majors. I know quite a few people that applied with a 3.35 and received a LOT of love. I'm a firm believer that most schools want more than just numbers and 3.35/30 will give you a solid shot. Try and do your best on the MCAT, and leave enough time to put together a solid app.
Your job as an applicant is to put together the most compelling application possible. Write a strong PS. I cannot stress that enough. Schools pick students for a reason. You've gotta show the school that you have a unique set of qualities that will benefit your classmates, faculty and medicine. The spanish will help you so talk about it, your extensive involvement with various ethnic/multicultural groups and committees will be an asset as well so make sure you put the right spin on it.
Also, try and create a story and a unifying theme that ties everything on your app together. Where have you been? where you are now? what did you learn on the way and how can you use this knowledge to achieve your future goals and advance the science and practice of medicine? Make sure your LORs are strong, they don't necessarily have to be from big name people, but people that know you WELL and can really highlight the strength of your character, intellect, diligence and personal skills.
Apply EARLY, apply smart, smile and you will do well.
Lastly, but most importantly, apply to UCSF. We'd love to have you.
Congrats on making it this far and good luck with the mcat.