H.,
I wrote this information a while back to another gal who was working on potty training. Hope this helps:
Here are some other considerations as to know when a child is ready to potty train. I took these excerpts from this great book on the subject called "Toilet Training in Less Than a Day."
Bladder Control: Do you notice that she urinates a good deal at one time rather than dribbling throughout the day? Does she stay dry for several hours? Does she appear to know when she is about to urinate as indicated by facial expressions or by specific postures she adopts? If yes to all three than she is aware of her bladder sensations and is ready to begin training. If she does the first two, she may still be ready for training, since not all children give this visible indication of their desire to urinate.
Physical Readiness: Does she have enough finger and hand coordination to pick up objects easily? Does she walk from room to room easily and without the need for assistance? If she does, she is sufficiently developed physically.
Instructional Readiness: To determine if your child has sufficient social responsiveness and understanding, ask her to carry out the following ten actions: Ask her to show you (point to) 1) her nose, 2) her eyes, 3) her mouth, 4) her hair. Ask her 5) to sit down on a chair, 6) to stand up, 7) to walk with you to a particular place, such as another room, 8) to imitate you in a simple task, such as playing patty-cake, 9) to bring you a familiar object, such as one of her toys, 10) to place one familiar object with another-for example, "Put the dolly in the wagon." If she carries out eight of these ten instructions, she should be considered intellectually ready for training.
If She Does Not Pass the Readiness Tests:
Most children over 20 months of age seem to be able to pass all of three of these tests. If your child does not pass the test for Bladder Control or Physical Development, you should wait until she has developed more coordination and more bladder control. Initial bladder control and physical coordination are very much a matter of simple maturation.
(There is some more about if she doesn't pass the instructional readiness test too if you want me to give you that information, let me know.)
Anyway, these guys did a lot of research on the subject and I think the key here is that if you want her to learn quickly and not have relapses that it is wise to wait until she is completely ready. My son is 3 and we just started him yesterday. It is working pretty nicely as he is able to pull his underwear up and down, which may be a more difficult skill for a younger one. The question you want to ask yourself is do you want to have to step in and help with various steps in the process or do you want her to do all the "potty" stuff herself? I think at a younger age, you will find that the former is true. When they are a little older, they will be able to do more for themselves and then it is not just a glorified diaper change with more work for you, but an independent act that they can do and feel good about too.
Good luck to you! I highly recommend buying the book. My mom used it when she trained my brother and I and said we were both trained in one day without any regression or problems afterward. The only thing I would say is that the book tells you not to have any toys or distractions while training. We ignored this advice and spent a day entertaining him in the kitchen dining room/area where there are wood floors and if he didn't want to "practice" (every 15-20 minutes or so) we would take some of the toys away and that worked wonders to motivate him. They advised to buy some "special drinks" that he would be encouraged to drink all day so that there were more opportunities to practice. That did the trick....we had lots of opportunities to say the least! And then we had M & M's to reward him (a couple at a time) when he did it successfully. (Those are two tips from the book also.)
Blessings,
H. C.