Delay feature on the Canon powershot A520?

No, you have to press the shutter release button to take the picture.
Press the FUNC/SET button. Use up/down to select Drive Mode (the rectangle, third item from the top). Use left/right to select the desired delay and press FUNC/SET. This sets the self-timer. Start the self-timer by pressing the shutter release button as usual.

Press the FUNC/SET button. Use up/down to select Drive Mode (the rectangle, third item from the top). Use left/right to select the desired delay and press FUNC/SET.

From the menu, select Drive Mode (third item from the top) then one of the self-timer options. Start the timer by pressing the shutter release button.

Once you've set the self-timer, start it by pressing the shutter release button as usual.

you can choose 2 or 10 seconds delay

Press the FUNC button. Use up/down to select Drive Mode (third from the top). Use left/right to choose the desired option (your choices are two seconds, ten seconds, and custom, which lets you select both the delay and the number of shots).

I also have this problem on a Canon A85. For some reason setting the camera to landscape allows the shutter and flash to work together properly.

1. Make sure the camera is in shooting mode (silhouette of camera)
2. Press Func/Set button
3. Scroll down to Drive Mode icon (usually single square)
4. Use left/right arrow to select 2-sec or 10-sec delay (clock with 2 or 10 next to it)
5. Press Func/Set button

Now whenever you press the shutter button, the camera will delay 2 or 10 seconds before snapping the picture. Remember to set back to single shot (single square) or continuous shooting (three overlaid squares) mode when done.

Press the 'drive mode' button to the left of the shutter button on top of the camera until you see a clockface icon with a 2, 10 or C in the upper center of the LCD (2 second delay, 10 second delay, or custom setting from menu).

Press the Function button and scroll down to the Drive Mode (3rd icon down on left side of LCD). Use the left or right button to select the self timer delay (2, 10 or custom). Press Function again and you're ready. (Remember to set back to single shot when you're done!)