Elderdog is 100% correct. Not having the site notice in place at the time the planning application is submitted (and for 5 weeks after) should lead to automatic rejection of the application as invalid. Similarly if the application is not submitted within 2 weeks of the press notice appearing in the paper, it will be invalid.
Planning authorities will usually be sticky about this, particularly if the office is busy (which they invariably are) as it is an easy way to claer their backlog.
Your guide in these matters should be the Planning and Development Regulations 2001 which you can view by going to
www.irishstatutebook.ie
Article 17 of these regulation states:
An applicant shall within the period of 2 weeks before the making of a planning application—
(a) give notice of the intention to make the application in a newspaper in accordance with article 18, and
(b) give notice of the intention to make the application by the erection or fixing of a site notice in accordance with article 19.
Articles 19 + 18 set out the information to be contained in and the appearance/fixing of the notice.
You should point out the above Regulations in your objection to the Council. If the site notice really wasn't up before the application was submitted then you should point out that the Council have no choice but to throw it back at the developer. The Council (and the developer) will know full well that An Bord Pleanala won't think twice about overturning any decision made by the council under these circumstances.
Of course, none of this will prevent the developer from applying again and getting it right. My advice is just to do your homework, read your county development plan fully and quote liberally from it (where it supports your arguments). The points you outlined above are a good start.
If your case is strong enough you should stick to your guns. There's enough terrible developments around the country already passed by planners with no vision.