Vandas will do great outside in your area during late spring, summer, and early fall. If you don't have any shadecloth (about 50%), hang them in the trees where they'll get dappled sunlight throughout the day with full sun in the early morning and early evening. They need a lot of light to prosper and bloom properly, but full midday sun will burn them. They're also very heavy feeders during the growing season so fertilizing twice weekly is good for them. Here, in midsummer, we water ours twice a day and fertilize two or even three times a week. (All of our Vandas are in teak baskets with exposed roots: no media).
The PREMIERE Vanda grower in the country is Robert Fuchs. He has more Vanda and Ascocenda hybrids to his name than just about anyone. The web address is http://www.rforchids.com
He's a little pricey, but the quality of his Vanda crosses can't be beat.