Ursula, I see your number #1 challenge as the rabbits, first, and the drought, second. Lilies can withstand long dry periods without water very well, provided there is enough foliage for minimum biological functions--and the plant will adjust the foliage it needs to do that. But, first you have to keep the rabbits out and give the plant a chance to grow full season.. And, besides, rabbits spread diseases, too, by their nibbling and chewing as the go from one plant to another. Many weeds and other plants that grow wild have virus and diseases also that rabbits can transport with their saliva so you must keep them out. Now, during you off season, is a good time to start making plans to put up a chicken wire fence--it doesn't take much and it doesn't need to be fancy to do the job.
As far as the drought conditions, a heavy 4 to 6 inch ( 10 to 15cm) mulch will really do a lot to hold moisture and to keep the soil cool. If you have lilies in pots, group them close together and then surround and cover the entire pots with mulch. Afternoon shade would be a big plus. Heavy mulching can cut your watering requirements by as much as 1/2 to 2/3rds.
