If you take the RER you'll have to change to Metro and still walk a bit to your hotel.
I would take the RER ( if that is what you wish to do)to St. Michel and a taxi from there to your hotel.
St. Michel RER stop is at the and of Boulevard St Michel near the river.
this may help:
http://www.ratp.info/orienter/cv/carteparis.php

sorry, at the end of B...not and

careful arranging a "car" to pick you up. Our flight(s) were delayed two hours and they first were out to dinner, then gone home for the day. Still charged us too.

If you can manage the luggage through two train changes, the fastest (and cheapest) way would be:

RER B to St-Michel
RER C to Invalides
Métro Ligne 8 to École Militaire

Map: http://www.ratp.info/orienter/f_plan...eur&fm=pdf

Thanks nbujic and Robespierre. If I am not entirely exhausted I think I'll give the RER/metro a go. I'm young(ish) and able-bodied, but sometimes a flight from California knocks the sense right out of me. However, I have no desire to sit in a taxi during rush hour.

You probably could take the RER to the Gare du Nord and from there the 42 bus to the École Militaire. Since the bus starts at the Gare du Nord, it might not be too difficult to get on with your luggage, and by the École Militaire it probably is empty enmoug to get off easily. It would give you a different tour of Paris.

For Rue Jacob, I'd probably take RER B to St-Michel and cab it from there.

Map: http://www.ratp.info/orienter/f_plan...eur&fm=pdf