For one thing, it is not too late to start from seed. I am preparing to sow 6 seeds each of over 180 varieties of tomato on April 1st, and my season is presumably even shorter than your since I am father north. I am relatively inexperienced growing tomatoes, but I have researched extensively over the past several months. If you do not mind hybrid tomatoes, for your hot and humid environmental conditions, I would recommend Mountain Glory F1 for a determinate slicing variety (good for short seasons as well as being bred for disease resistance and heat tolerance, Jasper F1 for a cherry tomato that is indestructible, and apparently JD's Special C-Tex is great for production in very hot summers. If you are shopping at your local store proven "early," "hardy," vigorous," "tolerant," and "resistant" varieties that are commonly sold include the "Bush" series of determinate tomatoes and the "Mountain" series that I mentioned one of (Mountian Glory.) Most of the great indeterminate varieties are by nature late season. The two indeterminate heirloom main season varieties that I repeatedly hear great things about are cosmonaut volkov and boxcar willie. To be honest though... I only have "research" experience.