Since they are outside the statutory time period you shoudl be fine for citzienship provided you have completed all terms of your sentence or probation. To properly advise you an attorney will need to review certified copies of each fo the court records for these and any other incidents.
Lynne R. Feldman, Attorney at Law
Formerly Adjunct Professor -- Immigration law
University of Illinois College of Law
To be eligible for naturalization you must have "good moral character" for the statutory period preceding your application for citizenship (3 years if you are married to a US citizen, five years for all other applicants. DUIs are generally not classified as crimes involving moral turpitude. Since it's been 15 years since your DUI convictions, you shouldn't have any issues with those DUIs.
Please note, however, that USCIS can look beyond those five years for convictions that may affect your good moral character, or even acts where no formal arrest or conviction took place. Because the application for naturalization is very delicate in nature, I always recommend you have an experienced attorney give you the go-head before your application gets filed.