Fill Flash on Av, 430EXII, 60D Help
To add to what Lemming51 has already stated, it doesn't matter what shooting mode you are in, the sync speed for a 60D is 1/250th of a second. That being said, if you do go into high-speed sync mode, know that you will lose about 2 stops of light from your flash. If you've set the flash to ETTL mode, it should compensate for the loss (assuming you aren't close to full power). If the flash is set to manual, you'll need to bump the power yourself.