Hi,

I'm from Croatia.. if you wanna retire here, I'd suggest you to first spend some time all year round in Cro, so you can get idea about life here (weather, people, government etc.) before making final move.
In general croatians have very positive opinion about americans, and very probably you woldn't have any problems because of your nationality.

now economy..., it sucks, but if you have like your own place and $2000/month retirement, 2 persons can live pretty comfortably with that.
real estate is pretty expensive, better said - overpriced. but you can rent it over summer and get some additional income. and also I'm not sure if americans can buy real estate here.. I think EU citizens can, but I'm not sure for others..

another problem that comes to my mind is visa. as far as i know, it is next to impossible to get some kind of permanent residency here.
it's possible US citizens have some kind of privilege though..

croatian language is pretty tough to learn for foreigners, and even more - we have 3 dialects, even I cannot understand good part of dialect spoken on coast, mainly because natives there don't make effort to speak official one
english is spoken mostly by youth.. older people, unless highly educated, have no clue.

check everything out, and decide.. mediteranean coast has plenty of choices