Most cyclists I see on the street can stop at the red light staying on the seat with one foot on the ground, while I was busying with dismounting and mounting (this is Manhattan with a red light every few blocks).
Then it's safe to say most of the cyclists you see have their seats much too low. Properly adjusted, you should not be able to put your foot on the ground while seated unless you lean the bike very far over.
The only way to avoid dismounting in traffic is to: a)time your riding to catch the lights green, or b) run all the red lights or c) learn to do a trackstand.
