For most of us in the United States growing outdoors is confined to those times when the temperatures are warm enough to move our plants outdoors for a few months of rest and relaxation for the plants. This time outdoors is generally very good for your plants and provides them with a big boost of energy caused by a number of different environmental factors. The light, if they are placed properly outdoors, will be much better than most of us can provide indoors. The day/night temperature differential provided by nature is very good for plants since that is the way they grow in the wild. Rainwater in most parts of the world is much better for plants than any kind of tap water and can provide a real improvement in growth.
Unless you have trees that you can use to hang your orchids, you will have to provide a growing area where your plants are protected from mid-day sun (unless you are growing Cymbidiums and Vandas which need full sun). For some good ideas visit Broward Orchid Supply which has a gallery of great outdoor growing areas. Note that most of these keep the plants off the ground in order to protect them from damage from slugs and snails. Another great site to see orchids outdoors is Roberta’s Orchid Central which showcases her Southern Coastal California orchid growing areas. She has some good ideas you might be interested in using. She has pictures of both sun and shade areas for various kinds of orchids.
Light filtering is one of the most important factors in growing outdoors. Most orchids cannot handle full mid-day sun and will need tree cover, lattice, shade cloth or some other mechanical filtering device. Be sure that you place your plants near a water source so that it will be easy to water when you need to. Think carefully about placing orchids on the ground. If you do so, be sure to pre-treat for slugs and snails and keep up a preventative program of slug bait around the pots. Do not put bait in the pots as some are poisonous to orchids. Ants can be another problem for outdoor plants so a preventative application of Diatomaceous Earth (DE) in the pots as well as a maintenance program for ants around the pots should be maintained. The ants themselves do not harm the plants, but they are a vector for aphids and other sucking insects which will harm leaves and flowers.