As long as your plants aren't getting a direct A/C blast, they should be fine. I finally relented this weekend when the temp in the house reached 28° and my husband threatened divorce. So we took it down to 27, and he's a bit happier. The orchids haven't noticed.
Generally, the plants will be ok as long as the change is gradual. If you keep the place freezing, like Isurus79, they won't grow as fast as at warmer temps. But they won't die, either.