If this is not close to a walking path I might suggest sugarcane, it should be ideal for your climate, grows fast, and you can get all sorts of interesting colors, particularly in the heirloom varieties. Starter plants can be bought on ebay from $5 to $40 each depending on type. (starter cuttings can be even less, typically $15-$25 for 5-7 ready to plant cuttings). The downside to sugarcane is the sharp edged leaves, some varieties are worse than others. A benefit would be a never ending supply of sugarcane swizzle sticks, skewers and chewing cane, and juice if you get a good press.
Ike
p.s. careful selection of the right type for your space is important, some varieties grow 1-2 inches in diameter and 5-6 ft tall, others get up to 4-5 inches in diameter and can reach heights of 15-20 feet., some grow straight others are prone to cork screw.