Having trouble deciding what I should put as my intended major on college apps

From UCLA’s website about switching majors from LS to Engineering/CS, it will not be easy or guaranteed. Make sure whatever major you select, you will be happy staying in that major.

I am non-engineering student and am interested in changing my major to an HSSEAS major
HSSEAS Majors: Aerospace Engineering, Bioengineering, Chemical Engineering, Civil Engineering, Computer Science, Computer Science and Engineering, Electrical Engineering, Materials Engineering, Mechanical Engineering. (Students may not apply to change majors to Undeclared Engineering).

Due to the competitiveness of admissions, students admitted to UCLA as junior level transfers to a major outside of HSSEAS (e.g. Math) are not eligible for change of major or double major consideration with a HSSEAS major.
Freshman admit students entering their third year or later are not eligible to apply for a change of major.
Meeting the minimum criteria does not guarantee approval.
Students will NOT be approved more than one change of major to a HSSEAS major. Students are encouraged to research the various engineering disciplines thoroughly before filing for change of major.
You may attend a change of major workshop if you have questions or would like some recommendations on alternate major options on campus.
Double majoring with an HSSEAS major: A student whose current major is in the College of Letters & Science would need to meet the eligibility requirements as described below to change their primary major to HSSEAS and then request to add double major.

To be eligible to change your major into Engineering you must fulfill the following requirements.
(1) Enrolling in an “Engineering Course load” aka at least 1 Math and 1 Science/Engineering course from the listed prep courses per term while enrolled in a minimum of 12 units per term
First year students may apply after completing at least 2 quarters that meet this workload
Second year students may apply after completing at least 3 quarters that meet this workload
See Prep courses as defined below and the Change of major FAQ for more clarification

(2) Earning a 3.500 GPA in the Prep courses enrolled. Students who are applying for Materials Engineering or Civil Engineering are eligible with a 3.000 GPA in the Prep courses. Students who are applying for Electrical Engineering are eligible with a 3.400 GPA in the in the Prep courses.
Students applying to the following majors must ADDITIONALLY:
(Please note that it may take additional quarters to change your major to these majors)

Computer Science or Computer Science & Engineering majors.
Effective F17, Students applying to Computer Science or Computer Science and Engineering must meet all criteria and additionally complete COM SCI 31 with a C or better (not a C-) on the first attempt AND COM SCI 32 and 33 with B- grades or better on the first attempt. This is a firm requirement.Note: Only one change of major from the College of Letters & Science is permitted and subsequent requests to change to a different HSSEAS major will be denied.

Preparatory Courses:
Listed below are the Engineering Prep Courses referred to many times in the eligibility requirement.

Be sure as you are building your Quarterly workloads that you are including at least one Math course and one Science course MINIMUM from the major that you are applying to. For more clarification, please see the Change of Major FAQ

Prep courses that apply to ALL HSSEAS MAJORS:

MATH 31A, 31B, 32A, 32B, 33A, 33B, PHYSICS 1A, 1B, 1C and CHEM 20A (CHEM is no longer required for computer science and computer science and engineering)

Additional prep courses specific to individual HSSEAS MAJORS:

(You are advised to refer to the HSSEAS Announcement for details on major requirements)Computer Science/Computer Science and Engineering – PHYSICS 4AL, 4BL, MATH 61, COM SCI 31, COM SCI 32, and COM SCI 33 (if a change of major is approved, the combination of COMPTNG 10A & B can be petitioned for CS 31. The combination of COMPTNG 10A, B, & C can be petitioned for CS 31 & 32. The combination of CS 31 & COMPTNG 10C will not be accepted). See Change of major FAQ for more clarification