Depends a lot on your personal circumstances and why you want an IR. If you have reasons for wanting both an FAA and an EASA IR (eg flying N-reg in Europe) then it can make sense. If the timings / availability work in terms of tying in with your holiday that it might make sense (though an IR is lots of work so you won't get much "holiday"!).
Your best bet would be to look at the cost of your FAA IR then speak to schools in Europe who can take you through a CBIR. Once you have done that you can decide whether it makes sense for you.