There is no exact science in deterring rabbits.  I have personally witnessed these critters eating rabbit-proof and toxic plants in periods of drought.  One morning, on my way to work I watched one jump four feet in the air grabbing tree branches to satisfy his appetite.  However, there are some things you can do and several products are available to reduce rabbit damage, but none are 100% effective. 

Some people use wire fencing and cages around their plants, but this is an expensive and unsightly solution.  The use of blood meal or Liquid Fence™ around the base of your plants has had some success.  The problem with these products is that you have to reapply every time it rains.  I prefer to plant plants with pungent fragrances such as rosemary, salvia clevelandii, autumn sage, or blackfoot daises near my colorful ornamentals.  Rabbits do no like the smell of these plants and will avoid the areas where they are planted.   Other plants that rabbits avoid are those of the euphorbia family, senna family, plants like Mexican honeysuckle (which in itself is a very lush and colorful desert dweller), and cacti with large amounts of thorns. 

As for your drip system, rabbits and other rodents chew your exposed emitters to hydrate themselves during periods of drought when other water sources and vegetation are scarce.