I see you are in Florida. There are some schools in Florida that will get you both your FAA and JAA licenses (the JAA IR still has to be done in Europe but at reduced hours if you have a FAA IR). If you only got FAA ratings now, you would have to do the conversion in the future, if you decided to move to Europe and believe me, the conversion is a pain in the backside. Since you have dual citizenship, getting both FAA and JAA would open some doors/options for you.
As far as doing your JAA in Spain, I would recommend you only consider it for your IR or if the school will get you a license outside of Spain's DGCA (Spanish CAA/FAAequivalent). The Spanish DGCA is notoriously slow and they have additional restrictions currently to some licenses that just become a nuisance. Even though I live in Spain, I fly to the UK occasionally so that I can deal with the UK CAA instead. In Jerez, there is a UK FTO called FTE, so if you are determined to get your JAA ratings in Spain, it is possible without dealing with the DGCA.