As you get to know your pig's personality, you'll learn that each cavy has their own method of communicating. One time it pays to be attentive is during cuddle time - all the better to avoid a wet lap. My girls use a few common signals to get their point across when they're ready to go home.
Poof and Revy are pretty good about holding it in. Gentle nibbles are their way of letting us know they need to go, "Bathroom, stat!" Peaches and Belka prefer to demonstrate their athletic prowess by forcefully tugging at the nearest cloth or worse, shirt.
Little Truffle and Abby-Roo become quite fidgety, occasionally even climbing up my arm. Truffle likes to take it a step further by circling and dropping warning beans. Although in her case it isn't because she wants to go to the bathroom, but because she's had enough of cuddling.
Sometimes the pigs will employ several signals at once, combining vigorous yanks with the occasional chatter in between. You can see their expression, "Move FASTER, human!"
How do your pigs communicate that they're ready to go?