It's easier to take them in your hands and find them a good home then leaving them to live in horrible conditions, it might just take a little time.
Or look around for a home for the goldfish & pleco, then take them off your friend's hands when you do?
It's really not that hard to do a water change and feed a fish, it would only take up to 15-20 minutes, especially with only one tank. Easier if it's only 10 percent everyday of the week and on the weekends, and clean gravel & water on weekends.
You could try talking to them about it. Find easy ways for them to take care of their fish while you find a good home.
Hope it all works out!
"Life is an adventure full of beautiful things, and a treasure worth more than gold."