I used to always use Schallers, but decided to go the cheap route. I now use the neoprene washers from the hardware store. They cost about .49 cents each. Just put your strap over the button, then put the flexible washer over the strap onto the button. Works like a charm. Just be sure the diameter of the hole in the center of the washer is smaller than the head of the strap button. It'll stretch out over the button, then resume it's shape, thereby keeping the strap from slipping off.
To answer your question, yes, you can use a strap on the Schaller buttons without using the locking mechanism attached to the strap. BUT... Since the Schaller buttons on the bass have a smaller head than older vintage strap buttons, you DO run a bigger risk of the strap slipping off. That's why I'd recommend these neoprene washers if you don't want to use the locks themselves. Here's how it would look:
