Ok so if I apply to Cal Poly SLO as undeclared, is it possible for me to become a mechanical engineering major? If it is, what steps should I expect to take in the future?
SLO does not offer Undeclared as a major option. You need to select a major when applying. You can select General Engineering and then ME later. If ME is your first choice major, I suggest you apply directly.
http://catalog.calpoly.edu/collegesandprograms/collegeofengineering/generalengineering/#undergraduatetext
Link on changing majors within the College of Engineering;
https://eadvise.calpoly.edu/Changing-Majors/Within-the-College-of-Engineering
Here is information of changing into Engineering from another College: https://eadvise.calpoly.edu/changing-majors/from-outside-the-college-of-engineering
The condition listed below is important in that you need to meet the MCA Engineering threshold as a Freshman applicant if you intend to change majors, so apply directly.
**Students must have been eligible for their intended major upon entry to Cal Poly (via the admissions process). See process below to determine eligibility for an intended major.
Cal Poly does this expressly to prevent exactly what you are considering doing, backdooring into a major you wouldn’t have been admitted into in the first place. Now, I don’t know you personally aren’t competitive to be a ME. That’s just why they do it. If your stats are not competitive for ME, GE, which is also getting very competitive, is the best route. They expect their students to change and lower the barriers into other majors. For example a GE only needs a 2.0 to be eligible to switch to ME while everyone else needs a 2.75. Good luck.
Thanks!