Can he pull his pants up and down (this really only matters if you have a younger child to take care of too)? If he can't (and if you do have a baby), then don't potty train right now. You can always make up a sign for potty (or use the real sign if you know it). That can help for when he can't speak.
This might be crossing over into info you're not asking for, so if so, just stop reading now...hehe
I have four kidlets now. I've tried potty training at age 2, and by child #3, I realized I'm wasting my energy to try at age 2. Not saying it won't work. it will. I've had my son trained at age 2...but the amount of work involved to train him AND the amount of work involved to help him go to the potty each time was just silly compared to how much easier it is when they train when they are three (when he trained at 2, I felt like I was the main one potty trained, not him...even though he was).
All of mine have become interested at age 2. Now I let them explore it and will see if they become more interested on their own. Usually all they want to do is explore. My 3rd just potty trained. It was SO EASY. She had maybe two accidents and was potty trained within a few days. It took a week or so for me to feel confidient that she really was trained. But she does it all herself. She doesn't have to rely on me for anything, except wiping when she goes #2. This works well for me since I have a baby and am prego with #5.
And, whenever you do potty train, I've had the best success with bare bummed potty training:-) You put nothing on them (other than a shirt if they want), have them sit on towels when on the couch/chairs, etc, and they seem to be a lot more aware than when they have anything else on. They potty train fast!
But back to your actual question - doing the potty sign can work to communicate. My first wasn't speaking much at all at age 3 when she potty trained. We signed.