2 flashes

[Robin Usagani]

I just bought a cowboy trigger. It is pretty cool. But now I want to do more. I want to start shooting with maybe one on the camera with lower power, and one off the camera from the side. My question is, how well do these canon flashes communicate to one another? What if the off camera flash is almost next to me? Will it trigger? Is there other method you think I should try that is more reliable? If I use infra red, I can still use the ETTL techonology or I have to go manual? I am planning to do manual anyway but just wondering.