I encourage you to direct seed most of your vegetables. I only start a few indoors, such as tomatoes and peppers.

I have no experience gardening in your climate but the temperatures seem about right.

Jim

The vegetables/herbs you list grow better direct sown than transplanted. All three have a tendency to bolt unless either direct sown or transplanted at a very early stage. Your temps would be mid summer in my climate. Plenty warm enough for the items you list.

What you just mentioned I would grow directly in the garden. Check out some of the Maricopa County calenders for planting dates but right now is perfect timing.
There is plenty of other things you could plant, too if you'd like. Chard, kale and collards last a lot loger than spinach when the heat of the spring hits. Beets do really well in our high pH and you can eat the greens like chard. We eat stir fried chard with eggs for breakfast most mornings.
Mustards and lettuce do great right now. Stir fry mixes also do well, as do peas. If you've never tried garden fresh peas you're in for a treat.

Chard is a terrific vegetable to grow. It is productive, foolproof and delicious. As Tracy says, it can tolerate much more heat than spinach.

Jim