Yes, I'd agree with that - a long masonry drill (8 mm x 250mm) for the cable and either sink a couple of metal boxes into the wall for an RJ45 faceplate, or just use surface mounting boxes (quicker, but a bit more obtrusive). Ideally you should use exterior grade Cat5 which is a bit pricy, but if the cable is protected (particularly from sunlight) then you could probably get away with interior cable - but use solid core rather than the more more flexible stranded cable, it is designed for backbone applications and is physically a bit more robust.