How much do you call cheap? I know many of the Dublin hotels, one in particular that I can recommend but you did not say if it was just to get a bed or for a visit to the city to sight see or whatever. If the latter they would be advised to stay in the heart of the city, no taxi fares to be taken into account and close to railway stations or what ever they need. If you can tell me what they are looking for I will gladly give you some hotel names. Is 70 pounds for 2 too much or how much do they want to spend per night?