This is coming from someone whose kid is not yet at bike riding stage, so take with a grain of salt...
I've heard that training wheels don't actually teach your kid to ride, b/c they provide too much support & therefore the kid is not balancing on his/her own. It's recommended to lower the seat so the child's feet touch the ground, so they can practice balancing but then quickly put their feet down if they need to. You can also take the pedals off (easily done with a tool called a pedal wrench, a bike shop could do it for you in 2 minutes) to get the pedals out of the way while they're learning to balance (essentially turning it into a balance bike).
DH is a cyclist & this is what he was told by his cyclist buddies.
Jen, mom to "Little Miss Tiny" 4/07