My Chances??

4.6 weighted
3.9 unweighted
33 ACT (30 Eng/ 35 math/ 36 read/ 30 sci)

EC:
-National Honor Society
-California Scholarship Federation
-Laguna Canyon Foundation (local volunteering)
-Scholar Athlete (2 years) highest gpa on basketball team
-Mentoring kids for basketball (2 years)

Major:
Civil/mechanical/aerospace engineering

Colleges:
Cal Poly San Luis Obispo
CU Boulder
Colorado School of Mines
Colorado State University
UC Davis
UC San Diego
UC Santa Barbara

And 1st decile ranking at my school (top 10%)

UC GPA? https://rogerhub.com/gpa-calculator-uc/
Post capped weighted and Fully weighted.

SLO GPA= UC capped weighted GOA with 9th grades.
Then calculate your MCA points.
https://mca.netlify.com/

You need safeties.

UC: 4.5 weighted
4.3 capped weighted

SLO GPA: 4.36
MCA: 4578

ACT: 34 superscore

Your MCA points look low for having competitive stats. Around a 4700+ is usually needed for Engineering majors.
UCD,UCSD and UCSB are definitely within Reach based on your stats. You need some safety schools: UC Santa Cruz, Riverside, San Diego state or Long Beach state might be good options

2018 Freshman admit rates for UC GPA of 4.20 or above capped weighted and not major specific:
UCB: 37%
UCLA: 41%
UCSD: 70%
UCSB: 80%
UCD: 89%
UCI: 75%
UCSC: 92%
UCR: 96%
UCM: 98%

2018 UC capped weighted GPA averages:
UCB: 4.23
UCLA: 4.23
UCSD: 4.16
UCSB: 4.13
UCI: 4.13
UCD: 4.11
UCSC: 3.96
UCR: 3.81
UCM: 3.71

25th - 75th percentiles for ACT:
UCB: 30-35
UCLA: 31-35
UCSD: 28-34
UCSB: 28-34
UCD: 26-33
UCI: 26-33
UCSC: 26-32
UCR: 22-30
UCM: 19-26

I actually messed up the MCA, its a 4728

A 4728 would be competitive for Civil Engineering. ME and Aerospace are tougher but definitely in the running. On this link you can search for major MCA’s by using the magnifying glass in the top right corner. Type in a key word and search. Each post with the keyword will be displayed.

http://talk.qa.collegeconfidential.com/cal-poly-san-luis-obispo/2128373-cal-poly-slo-2019-final-status.html