San Diego gardener here. Depending on how normal/abnormal our summer will be (who knows, it's been a crazy winter) it's not too late to plant tomato transplants. If you're wanting to plant from seed, I'd wait to start them in mid-late June for fall tomatoes. I generally plant out in early/mid March, and then do a fall planting around Septemberish for a fall/winter crop.
There are a lot of things out here that can affect how well or poorly your tomatoes do, and a lot of them are very micro-climate specific. We have a lot of annoying insect pests in my micro-climate that can make getting a good tomato crop difficult, depending on the year. Aphids have been particularly heavy this spring, and I normally get thwacked pretty hard by thrips and spider mites starting in late June/early July...expecting that to be particularly bad this year with how rainy it's been. All of those can heavily affect fruit set and plant mortality depending on how stressed your plants get. One of the reasons I have a small fall crop go in to replace insect killed plants after the majority of those insects are gone. Anyway, keep an eye on your plants for tiny little bugs, they can make a huge difference in productivity and plant health here.
Even in super hot summer weather, you shouldn't have to water every day unless your soil is just sand (and in that case, make sure you're not also dealing with root knot nematodes which can be a nightmare - some areas of my yard are awful for that). Water infrequently and deeply, much better than frequent, shallow watering. I also wouldn't bother with shade cloth...it's not the sun's heat hurting the plants, it's just that fruit won't set in that temperature range. Shading likely won't help that much.
Varieties - Cherries will almost always do well, even in the really hot part of summer. I'm suspecting that other varieties are VERY individual garden/micro-climate specific. I have a gardening friend that lives 10 miles away who grows amazing Cherokee Purples - these end up being the sickliest and worst producing plants in my garden, even when planted from the same source. Look for varieties that look good to you and experiment if you can't find a gardener very near you with hard suggestions.
Also, something I picked up here last year - using an electric toothbrush to "hand pollinate" your blooms will increase fruit set dramatically. I easily doubled the tomatoes I got last year with the same number of plants by just hitting the blossoms with the toothbrush once a day.
Q