Get rid of the pull ups. The other mom (I'm sorry...can't recall the name) was right when she said that they just hold the kids back. Make sure he knows that there will be no more pulls ups in the house at all. I know some might disagree with me, but don't even keep some for night-time because then he'll hold his movements until then. Let him run around the house in just his underwear, that way there's less for him to get out of the way when he does go. Ask him every 30 mins or so if he needs to go potty, or take him to the potty if you like. Make sure that he's well praised when he does go to the potty, and double the praise when HE tells you that he has to go. If he has an accicdent, let him be the one responsible for cleaning it up. He's old enough to change his own underwear, use a towel to wipe up wet messes, and rinse out the dirty ones.
On a side note...are you using a potty chair, or a potty seat? Neither one of my boys liked the potty chair at all and prefered to go on the "big" potty like mommy and daddy. Also, those stupid splash guards that they put on the seats and chairs are a nusance at best for little boys, and a pain in the butt when you have to fish it out for the 45th time in one day-- get rid of it. He may be afraid of "catching" himself on it.
If you're looking to put him into a public preschool, they should offer assistance with potty training. Talk to the teachers and see. That was one of the questions asked when I enrolled my boys, and I was told that the teachers will work with the child if needed.
My oldest son was 3, and my youngest was 3 and 1/2 when they were trained, so I feel your pain!