Hi! Try it or not - if he is ready, he'll do it, if he isn't ready, he won't.
HOWEVER - in my humble opinion, I wouldn't do it. Simply because once he's potty trained, he will want to go to the potty in EVERY public place you ever go to. Trust me, they all do! They want to check out the restrooms, for some reason. I don't know WHAT they think they will find - a different toilet, maybe? But it won't matter if he just went right before you left the house, and the store is only five minutes away. Once he sees a restroom sign - and oh, yes, they learn to recognize it quickly! - he will say he has to go. :)
And let me tell you, helping a child (because he will still need help, especially in the disgusting restrooms where you don't want him to touch anything) in a public restroom, with a baby in tow, is NOT a fun thing to do. :) So, take time to consider how it will affect YOU, if you do it.
Also, remember how children backslide sometimes when a sibling comes along. You may get him potty trained, all for naught, if he decides to use diapers again like that new baby who is getting so much attention! :)
Best of luck! And congrats on the new baby!
J.