Answer: There's a perennial morning glory (Ipomoea acuminata) that fits the description and is especially well suited to your growing zone (actually zones 8 & 9)so I suspect that's the plant you're seeing. It's a vigorous, rapid grower, reaching 15'-30' with dark green leaves and bright blue trumpet shaped flowers. It blooms in one year from seed and grows from cuttings, division and layering of established plants.
Seeds are difficult to find, but a local nursery should carry the plants. Enjoy!
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