When I look at gear lists, I like to see everything that will be carried on a typical trip with the base gear. For example how long is the typical trip, how much food and water are needed.
I see you have 3 liters in water bottles. Will you be carrying that much water? Probably yes in Southern Cal, but not in the Southern Sierras.
Where will you be hiking? If in the San Bernardinos or Southern Sierras, you usually need some sort of plan for bears... either a hang or canister.
I see you are a student, so some suggestions may not work if you do not have a lot of money to spend of gear. If you do, that is great.
You said 2-3 days. If so, your pack is way too big! You can cut your base by nearly a pound if you switch to a GG Murmur. The Murmur will work fine (as in comfortable) as long as you do not need to carry much water, and you can keep the total pack weight under 10 lbs.
Why are you carrying a rain jacket if you expect no rain? A wind jacket is much lighter.
Don't count on the weatherman in Southern Calif either. On Memorial Day weekend four of us started on a trip with zero chance of precipitation. By 4PM a freak storm came in and our intended destination got snow and 90 MPH winds. But if you are completely sure of no rain, you do not need the trash compacter bag.
I would suggest you bring a poncho/tarp for possible rain and shelter in the mountains. You could probably get by without a bivy, since your quilt is cuben and is waterproof except for the sewn seams. You are only concerned with spray the poncho/tarp can't catch. But I have to admit that on many local summer trips I am so sure of rain I don't bring anything for rain either.
I don't see first aid kit, map or compass.
You can save a little weight by going with Caldera Cone/Keg/Esbit set-up.
Aqua Mira tablets are lighter, easier to use, more concentrated, but more expensive. You save 2 oz because you do not need the mini droppers.
There are lighter down jackets that will be fine for summer such as a Montbel Ex UL. Usually in the summer in the San Jacintos or San Bernardinos I often don't take a jacket at all. If it gets chilly at night before I go to bed, I just wrap the quilt around me.
Take a look at my gear list in my profile. It is even lighter, and there is much more gear to make life comfortable. There are a few items I carried in my pockets, which some people would keep in their pack. That gear list is 2 years old, and some of the gear I have bought since is even lighter. Today if I use the Murmur I can have a large tarp and rain jacket with a total base under 4 lbs for a 3 day trip. I have done some summer trips in the local mountains with a sub 3 base weight. Just keep in mind that if the total pack weight with consumables is over 10 lbs, I am not taking the Murmur anymore.