Yes, if you can get a good plastic lily (or silk, if you prefer) then it is reasonable deer proof, but no guarantees even here. If you are thinking of planting real plants (live lilies) then be preparred to spray deer-off vigorously because the deer love lilies. It is an all time favorite.

Asiatics are the easiest to grow, and the bloom early and reproduce prolifically. Orientals bloom later and can be a bit iffy in your zone if not mulched. Worst case, the really slow movers can bloom too late if you have a very cold spring and an early fall frost. The plants may not be able to bloom before first frost especially if planted in an area which stays relatively cool (north side of fence, etc) in spring. If a southern exposure which gets warm fast in spring, orientals may do ok with mulch.

Orienpets are mixes between orientals and trumpets. A better choice for your area would be the LA lily (Longifolium X Asiatic) which are crosses between easter lilies and asiatics are extremely prolific, very hardy in cold zones, and will give you many lilies in a short time.

For your zone, my preference would be LA Lilies, Asiatics, Orientals, Orienpets in that order. Don't forget the species lilies, either.

Thanks for the helpful info. I am not really surprised that deer love lilies, since they seem to like everything I grow. Actually, woodchucks seem to be a bigger problem for me. And they eat all the plants that are supposedly deer resistant. So, I guess I just have to keep spraying everything.