The tree will be planted in-ground. A Moro, probably on C-35, from Menlo Growers (thanks for the pointer, Badfish8696). We're in 9b (Sunset 14). C-35 is the only non-dwarfing rootstock I've found that we can get here in a quarantine-free zone in Northern California. I'm not sure about the soil, this is for a friend on the other side of town. I know she has very little patience and a bigger tree will look better in her eyes.
On a related note, when's the best time to plant a citrus tree (yes, I know, ten years ago)? But seriously, we've been hitting 108 degrees this week and I can't imagine now being a good time.