Depends on how long you are going out of town.
If it's for 2-4 days, I wouldn't worry about it. If the tank is established enough, and you have algae and a good amount of LR, they will be fine.
Anylonger, and you'll need to enlist a friend to come by and feed for you. I'd stay away from the auto-feeders, my experience with them is that they are more trouble than good