Bob discusses some methods for hanging and attaching signs to EIF systems.
It's quite common for outdoor signs to be used in conjunction with EIFS. Often, signs are in direct contact with an EIFS wall or are somehow connected to it or through it. In fact, you can make signs themselves out of EIFS but that's another story.
One of the key issues regarding to installing signs on EIFS is simple: How big and heavy can it be before it cannot be attached to the EIFS? In other words, when must a sign be attached through an EIFS? The answer is also simple: Except for the lightweight materials described above, all "signs" should be attached through the EIFS. "Through the EIFS" means all the way through to a structural member behind the EIFS. This does not mean attaching to gypsum-based sheathing, which is not a structural material from a sign attachment standpoint. Rather, attachments should be made to structural materials like wood studs, metal studs, concrete, block or a structural type of sheathing like plywood.