Booklady-
If you don't want to give up your Am. citizenship and want to retire in Spain for a few years- you will have to go through the regular process of getting a residence visa- a special one for retirement regardtheless if your parents and grandparents were Spanish.
Here is the info you need on the retirement visa. Its not really a big deal- even the paperwork is simple- as anything it takes time- that's all- but it still would if you decided to apply for citizenship. Now, your parents were(or are) Spanish- but were they born there. That makes a difference if you decide to apply for citizenship- let me know and I can give you the info for that option also. The spainconsul-ny.org website is the best one in the US for getting information as far as what will be required- but ultimately you'll always have to go through the consulate in charge of your region, which in your case is Miami.
Here is the info from the website.
This visa allows a foreigner to reside in Spain as a retiree without working.
To apply for this visa the following requirements must be submitted in person:
Passport valid for a minimum of six months and three photocopies of the personal information and photo page.
4 recent pictures, passport size.
Original marriage certificate *.
Original certificate of good conduct issued by the police department of the city or cities where the applicant has spent 6 months or more in the last 5 years, with a translation into Spanish .
Original medical certificate typed on doctor�s stationary verifying that the applicant is free from the following quarantine diseases: yellow fever, cholera, and the plague. The certificate must also certify that the applicant is free of drug addictions and mental illness, with a translation into Spanish .
Original Medical Insurance that will cover you in Spain.
Original certificate of a public or private institution certifying that you receive a pension, specifying its monthly amount.
Proof of any other source of income and/or properties in Spain (The anual minimum is $10,000 increased by $1,700 for each dependant).
If you own any propety in Spain you must bring Original proof of ownership.
If you are not a U.S. Citizen, bring your green card.
It is also necessary to submit two (2) photocopies of all the documents.
*Documents must have the Apostille of the Hague Convenction
The resolution of your application might take up to 6 weeks. Be advised that special conditions for certain cases may apply.
Let me know if you want more information or info regarding the option you have as per getting Spanish nationality.

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