You should ask Mr. Keenan about deferrals...I don't think that is a common practice in Ireland, and don't know if they'd be receptive to it. I don't really see how that would hinder Irish school acceptance because you'd be on a student visa here. Do you mean you are getting a US Green card, and you need to be in the US for the 2005 year?
I'm not married myself, but one of my classmates is married and others brought their girlfriends with them (and are now engaged). They don't have problems here, but the trick is for your spouse to find work, which would be harder problem than you attending medical school
. Expect that you may have to be separated for a little while if your spouse has to attend further training courses (sometimes even back in the US, depending what field) in order to be qualified for a work visa here. I'm not sure about non EU teachers, but considering that teaching is always in demand...she might be able to find somewhere... However, I don't know how likely it is that a school will have money to sponsor non-EU work visas and she may have to absorb the cost herself... it really is a matter of researching and contacting different schools, which unfortunately could best be done once you arrive (meaning she'd be unemployed for awhile while searching for her options).