Potty Training for a shy puppy

Question
We've had our new 3 month old Olde English Bulldogge pup for about a week now. We noticed he's really shy around new sights and sounds but he is slowly building up his confidence. The main problem we're having with him is potty training. We have another 3 yr old female that is trained to use the dog door to go outside. We've been very consistent about going outside to the same spot but he is too nervous and scared to go potty that he won't go or he'll go half way (We live near a busy freeway and street). He has to have all of us (me, my boyfriend and our other dog) go outside with him. Or he will wait until we all go back inside and relieve himself. How can we train a shy puppy to go outside by himself or at least let us know?

Answer
One of the most important things is praise him when he goes.  The whole bunch of you rave about what a good dog he is.  He should be starting to accept his new home.  of course, 3 months if a little late.  They adjust much more quickly at 7-8 weeks.  Be generous with your praise for everything.  

Perhaps he would respond to the same confidence building techniques as I suggest for submissive wetting.  

Start with obedience training.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  As you praise the dog for following your commands, it will build its confidence.  

Play tug of war with the dog and lose.  However at the end of the game, take the rope or toy and put it up, less the dog becomes confused about who is top dog.
Ropes from the pets' store quickly turn to hazardous shreds.   Ones I made
lasted much better.   Go to a hardware or home center that sells rope by the
foot.  Buy 2' of 3/4" poly rope.   Melt the ends, and tie  knots in it.   Get
them as tight as possible, put it in a vise and pound it with a hammer.  Watch
carefully, and be ready to discard when it comes apart.

Finally, make sure it has a den to live in.  If you are not using a crate, buy one.  The dog may be happier in its den than loose in the house.  It relaxes, it feels safe in its den.  It rests, the body slows down reducing the need for water and relieving its self.  Dogs that have been crated all along do very well.  Many of them will rest in their crates even when the door is open.  I think the plastic ones give the dog more of a safe, enclosed den feeling.  Metal ones can be put in a corner or covered with something the dog can't pull in and chew.  Select a crate just big enough for the full grown dog to stretch out in.

A dog that has not been crated since it was little, may take some work.
Start out just putting its toys and treats in the crate.  Praise it for going
in.  Feed it in the crate.  This is also an easy way to maintain order at
feeding time for more than one dog.