There's a long thread on this forum about growing hot weather greens; I'm attaching the link. I'm trying a greens mix this summer like the OP of the attached thread suggests, beet greens, chard and kale, and I'm also branching out into shoots.

I've tried several types of lettuce and the one that seems to taste the best is Jericho. I'm currently growing Red Sails, New Red Fire, Green Deer Tongue, Sierra Batavian and a few others. None has bolted yet, but some have gotten too bitter for me. I put 50% shade cloth on my lettuce beds at the end of May, and I water regularly, but most lettuce goes too bitter for me anyway.

Sierra Batavian was a disappointment, as some say that it's a very good summer lettuce. I've had good luck with Green Deer Tongue before, but what I'm growing now is too bitter. Red Sails and New Red Fire are ok, but also on the bitter side. The Jericho is the best tasting lettuce that I have by far, so I'm tearing everything else out and concentrating on Jericho and the hot weather greens mix.

I'm also growing orach, which was good in the spring, tasted like a strong spinach, but has gotten too strong for me in the heat. It can take much warmer temps than spinach, so something you might want to try, but I prefer chard, beet greens and kale to the orach.

Here is a link that might be useful: Hot weather greens

Regular mizuna does well for me mixed with mostly Red Russian kale and mixed baby chard. I can add tatsoi in spring and fall. It is just better then spinach for bolting. For direct seeded lettuces, I have started with the summer mix from Fedco I believe and then saved seed from the last to bolt. As for transplanted lettuces, I am still doing trials. I actually do not like Jericho.
I cover all my greens with cheap shade fabric and keep them well watered and well weeded. The mizuna and Russian kale are just wonderful for cutting baby leaves several times a week.

last year as well as this year i'm growing salanova for summer lettuce. i have 2 greens (oakleaf & butterhead) and 2 reds (same kinds as green). a lot of irrigation helps.

Little Minnie, Do you find that white plastic mulch helps much?

It's been in the 90s here this week and I doubt that any of my lettuce is going to be any good. We'll see.

@ Rox, I'm in Houston. Don't bother with any type of lettuce in our summer heat even with shade cloth (unless you grow hydroponically or aquaponically). For micro greens: red Russian kale, radish (micro only), broccoli (micro only), mustard greens (they grow like a weed in TX). Regular greens: red malabar spinach (it is not a spinach), sweet potato greens (find the sweet potato vine grown specifically for leaves and not the potatoes.), red Russian kale (full size will survive but turn bitter in our heat). Don't bother with Asian greens (Pak Choy, tat soi, etc) until September. Swiss chard might work, my full size ones are surviving so far. Have u tried sprouts in instead of micro greens? Sprouts do very well at our markets. Also, try trays of Wheatgrass. I'm sure it will do very well in Austin.