Does anybody know if the YN-560 II flash can be triggered (in manual mode) by the Canon St-E2 infrared receiver (or even the infrared system on the 580 II if it was master on camera and you wanted to trigger the YN-560 as slave)?

Or does the YN-560 II only work as an optical slave?

I have an ST-E2 and 430EX II and want to use the 2 flashes together fired by the ST-E2. Again, not using ETTL just manual mode.

The ST/580 won't trigger it via infra, but you can use the 560II in manual mode+optical slave, so as you tigger the 430 with your ST, the YN560 will flash too.
Other option is to get the newer YN560EX (I put a short review here) who supports ETTL via infra red, therefor your ST will control it.
The YN560EX costs about 90$ but I think it worth the extra 20$ (over the YN560II)

Thanks Uzet1, that's exactly the information I was looking for!

uzet1 wrote: ...you can use the 560II in manual mode+optical slave, so as you tigger the 430 with your ST, the YN560 will flash too.

Won't the command & control preflashes of the ST-E2 cause a premature triggering of the YN560? Or can it be set to ignore the preflashes?

From what I understand, with the 560 and 560II there are 2 optical triggers, one for use when there is no preflash, and one for when there is.

But the YN560EX will work with infrared from the ST-E2 trigger just like a normal Canon flash, with TTL included! Just no HSS.