All depends what cacti they are, some need lower light levels to bloom, others need a lot more. If it something like a rebutia or gymnocalycium it would be ok as long as it doesn't get too hot. Sun coming thru glass can be really hot at times. It would be your fall there now and shouldn't be a problem until spring, I'm an Aussie you see, we have just the opposite seasons to you.

Thanks for the info! I've got four or five different kinds on the windowsill, but the only one I'm a little concerned about blooming is the Stapelia Variegata. Do you think that one will?