This is a moonflower. The plants are (supposedly) fast growing annuals that can create a quick screen. The bonus is the huge white flowers that open only at night and release a sweet fragrance.

In fact, the plants aren't fast enough here in Sacramento to form a screen until summer is over. By the time the plants are large enough to flower, it's no longer time to sit out on the patio and enjoy them. The plants aren't really annual, either - just very tender perennials that can't take any frost. So, we're seeing if we can keep the plants alive over winter and get them going again next summer.