Rosemary is always a nice choice, fragrant and pretty and will easily maintain at 3'. Bamboo to keep it that short you would be trimming weekly, and it can be invasive, it also drops leaves all the time.

You might want to try Summerwinds there is one in SJ, they have more knowledgeable staff who could help you out.

Boxwood is lovely but a very slow grower. Euonymus is okay but the Rhaphiolepsis, Indian Hawthorn, probably will work best. Don't get the dwarf varieties, they're more open. I can't say I particularly like Rhaphiolepsis trimmed as a hedge but it's common around here, especially in commercial plantings, and it grows very thick and impenetrable. They are reasonably xeric once established.

Heavenly bamboo is nandina, I assume? Don't grow it. Lovely but more vase-shaped; to be thick you would need to keep it at a higher height, around 4' or so. It sends out runners everywhere which is highly annoying.

There are many varieties of gardenia but the one most commonly sold is the trickiest to grow. And it won't make a good hedge. Rosemary is more open-form in its branching; you would need to be careful what variety you pick.

tinan is giving you good advice to talk to an independent nursery. Unlike big box centers, nursery staff are usually fairly knowledgeable. Tell them what your requirements are and ask who would be the best staffer to talk with.

I'm a novice gardener but I have tended rosemary for many years as I've always had a herb garden. There are many varieties. It smells fresh and lovely!

Here is a nice picture of a well trimmed rosemary hedge, kept low and full.

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Here is some upright rosemary growing untrimmed
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Thank you all for the great inputs! Looks like rosemary is a good choice. Can anyone recommend a good variety for hedging? I saw Tuscan Blue, Huntington Carpet, and Irene from a local nursery and it looks like Tuscan Blue looks better than the other as it is more upward and not as open.

Thanks again.

I have planted tuscan blue, it's a very nice variety and I think you will like it. You can either keep it neatly clipped (which will make it grow thicker too) or natural.

Rosemary is nice but keep in mind that it will get woody and bare at the base exactly like the juniper you had there.

Go with Indian Hawthorn, cheap, unfussy, tough as nails, you can't beat it for an easy low-care shortish shrub that requires little water once established.