If you’re going away for up to a week, they’ll be fine. Do a water change about 24 hours before you leave and clean things up a bit, feed them a little extra, (not any more than twice the normal) and they’ll do fine.
For up to two weeks, you’ll want someone to come in and feed them, maybe one feeding halfway into your vacation. For longer than that, you really need someone to come in and look after you fish.
If you have any friends that are willing, have or hire them to come in and feed the fish, turn on and off the lights if you have plants, and maybe do a water change.
Make sure they know EXACTLY how much to feed, and won’t overfeed just because they “look hungry.” Someone who already knows what they’re doing is always best.